Respiratory Syncytial Virus

What is RSV?

RSV stands for Respiratory Syncytial Virus. RSV is a common viral infection that peaks in the fall and winter causing mostly mild cold-like symptoms in healthy children and adults. In at-risk people, RSV has the potential to develop into a more serious lower respiratory infection, such as bronchiolitis or pneumonia.

Most infants recover from RSV within 1-2 weeks with rest and home care. More serious RSV infections may require a hospital stay and possibly supportive oxygen treatment. However, outcomes are good for most hospitalized infants and children who return home within 3-4 days (1).

Learn more about RSV from the CDC: Respiratory Syncytial Virus (RSV)

Who is at Risk of Severe RSV Infection?

RSV can be serious for some populations (1), including:

• Infants under 12 months of age
• American Indian & Alaska Native Children
• Children born prematurely
• Children with severe cystic fibrosis
• People with underlying heart and lung disease
• People with neuromuscular disorders – especially those who have difficulty with swallowing or clearing mucus secretions
• Immunocompromised people
• Adults over 65 years of age 

How is RSV Spread?

RSV is a very contagious infection. Most people have had RSV by the time they are two years old. Routes of infection include respiratory droplets (from someone coughing or sneezing near you), direct contact (e.g. from shaking hands, hugging, or kissing), and contact with dried secretions on surfaces like toys, countertops, bedding, etc. The virus can survive on hard surfaces (e.g. door knobs, shopping carts) for up to 6 hours and for shorter periods on soft surfaces (e.g. blankets, hands) (1-3).

Symptoms of RSV arise 4-6 days after contracting the virus. RSV is most contagious 3-8 days after symptoms appear. However, for some people (especially babies and immunocompromised people), viral shedding can occur for up to 4 weeks after symptoms disappear (1).

Symptoms of RSV in Adults, Children, & Older Infants

In healthy adults and children, symptoms of RSV are usually mild and indistinguishable from the common cold. Symptoms can include:

• Stuffy or runny nose
• Sneezing
• Headache
• Dry cough
• Sore throat
• Low-grade fever

Sometimes RSV can progress to a more severe infection of the lower respiratory tract resulting in pneumonia (inflammation of the air sacs of the lungs) or bronchiolitis (inflammation of the small airways of the lungs). In these cases, symptoms may include:

• Severe cough
• Wheezing (high pitched noise heard mostly on the exhale)
• Rapid breathing
• Difficulty breathing
• Fever
• Bluish color of the skin due to lack of oxygen 

Symptoms of RSV in Infants Under 6 Months

Symptoms of RSV appear differently in young infants and may be mild to severe. Signs and symptoms can include:

• Struggling to breathe (retractions* may be visible)
• Shallow, rapid breathing
• Cough
• Poor feeding
• Unusual tiredness
• Irritability
• Apnea (pauses in breathing of more than 10 seconds)
• Fever may or may not be present

*Retraction is a medical term for when the spaces between the ribs and in the neck sinks inward during an inhale. This is a sign of struggling to breathe. 

Serious Outcomes of RSV Infection

In infants under a year old, up to 40% of RSV cases progress from an upper respiratory infection to bronchiolitis (3).

A significant minority of infants and children with RSV bronchiolitis need to be hospitalized for RSV, with a lower age leading to a higher risk of hospitalization as seen in the chart below (4). The CDC estimates that RSV causes 58,000 to 80,000 hospitalizations per year in children under 5 years old (5). 

RSV is the leading cause of hospitalization in children under a year old in the United States. It accounts for approximately 10% of all hospitalizations in this age group (6). 

The overall risk of hospitalization due to RSV in children under 5 years old is 4 per 1,000 or 0.4% (4). 

Age of Child	Risk of Hospitalization
0-2 Months	23.8/1000
3-5 Months	13.4/1000
6-11 Months	7.6/1000
12-23 Months	3.9/1000
24-59 Months	1.0/1000
All Children Under 5 Years	4.0/1000

Hospitalization can be a scary event for families; however, outcomes are usually positive with most of those admitted being discharged within 3-4 days. Though risk for hospitalization is higher with prematurity and/or underlying conditions, it should be noted that in this study, 60% of children under 5 and 75% of children under 1 who were admitted to the hospital for RSV were otherwise healthy and had no underlying conditions (4). 

RSV as a Cause of Mortality in Infants

RSV is not a common cause of death in infants in high income countries like the United States. According to a recent study, 99.96% of hospitalized infants recover (7). According to CDC estimates, RSV causes 100 to 300 deaths per year in children under 5 years old and 6,000 to 10,000 deaths per year in adults over 65 years old (5). 

Worldwide, the mortality rate for RSV in infants is much higher. RSV is responsible for an estimated 100,000 deaths per year in children under 5 years old. 97% of these deaths occur in low-income and middle income countries (8). 

Long Term Effects of RSV Infection

There has been a lot of research into whether severe RSV infection in infancy causes long-term wheezing and/or asthma. Research is still ongoing, but the present belief is that RSV may be associated with the development of wheezing. There are questions of whether RSV is associated with the development of asthma later in life, but as more research is done, this seems less likely (3).  

Conventional Treatment of RSV

Most RSV infections and bronchiolitis do not require any specific medical intervention and can be managed at home with supportive care like any other mild respiratory infection. Supportive care includes rest, nasal suction, nasal lubrication, fever management, and hydration (3). 

Hospitalization is recommended for infants at high risk of severe disease, anyone with severe symptoms, those requiring IV fluids to treat dehydration, and those requiring respiratory support. In-hospital care may include supplemental oxygen, IV fluids, CPAP (continuous positive airway pressure), intubation, and mechanical ventilation (3). 

There is an antiviral medication approved for use against RSV — Ribavirin — but its use is controversial because of cost, questions of efficacy, and danger to exposed healthcare providers (3). 

RSV Protection Options for Infants

Parents have several options for reducing a child’s risk of severe RSV outcomes: 

1. Breastfeeding (if possible)
2. Abrysvo maternal vaccine during 32-36 weeks of pregnancy (September – January)
3. Nirsevimab monoclonal antibody injection after birth (infants born October – March)
4. Nirsevimab monoclonal antibody injection in October (infants born April – September)
5. Pazilivumab monoclonal antibody injection series after birth (high risk infants – only if Nirsevimab is unavailable)

Though the above strategies may help reduce the risk of developing severe RSV infection (see the efficacies of each below), they don’t fully eliminate all risk. Important strategies for reducing the risk of RSV regardless of immunization or breastfeeding status remain:

• Good handwashing
• Avoiding unnecessary exposure to germs during RSV season
• Limiting the people who hold and kiss your baby to close family members
• Cleaning surfaces regularly
• Keeping infant away from second hand smoke

Timing of RSV Immunizations

The timing of RSV immunizations and the immunization that you’re offered depends on the month your infant is born in and whether you live in an area with predictable RSV patterns. 

Abrysvo – RSV Vaccine

• Offered to women who are 32-36 weeks pregnant from September to January

Beyfortus – Nirsevimab RSV Monoclonal Antibody

• Offered at birth to infants born October – March
• Offered in October to infants born April – September

See this page and speak with your doctor for more information: Immunizations to Protect Infants | RSV | CDC

Protective Effect of Breastfeeding Against RSV Infection

Breastfeeding offers a protective effect against severe outcomes in infants with RSV infection, including risk of hospitalization and use of supplemental oxygen (9). 

The protective effect of breastfeeding doesn’t require exclusive breastfeeding; partially breastfed and donor milk supplemented infants also get some protection from severe RSV outcomes and hospitalization (9). 

Unfortunately, it isn’t possible at this point to confidently say that breastfeeding reduces the risk of severe RSV infection by a certain percent because studies vary considerably. To learn more, see this article: Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention.

About the RSV Vaccine in Pregnancy (Abrysvo)

Abrysvo is a vaccine recommended to pregnant women between 32-36 weeks of pregnancy in order to offer protection against RSV to infants in their first 6 months of life. Because RSV is a seasonal infection, the RSV vaccine is generally only administered from September to January in most parts of the United States. In areas with less predictable peaks (Hawaii, Alaska, Puerto Rico, etc) the vaccine may be offered all year. If an infant needs RSV protection outside of this timeframe, Nirsevimab (a monoclonal antibody for infants) is recommended. 

The RSV vaccine works by inducing the mother’s immune system to produce antibodies against RSV proteins. The antibodies offer protection against RSV to the mother. They are also transferred transplacentally to the infant where they provide protection for up to 6 months.

Abrysvo contains recombinant RSV protein + buffer ingredients. Abrysvo doesn’t contain preservatives. Abrysvo is not a live vaccine and cannot cause infection.   

FAQ: If a mother gets the RSV vaccine after birth, will she transfer protective antibodies through her breast milk?

Answer: At present, the RSV vaccine has not been studied in breastfeeding women, so we do not know if antibodies are passed through breast milk. It seems reasonable to believe that RSV antibodies created in response to the RSV vaccine would transfer through breast milk just like other antibodies do.  

We also do not know conclusively if the RSV vaccine is safe for breastfeeding mothers because there have been no studies directly looking at this question. However, the CDC doesn’t list breastfeeding as a contraindication for the vaccine. The belief is that the RSV vaccine would have a similar safety profile during breastfeeding as other non-live vaccines — such as TDaP — which are generally considered safe during breastfeeding (10).

FAQ: If a mother got the RSV vaccine in a previous pregnancy, should she get it again for her next pregnancy?

Answer: At present the recommendation is to not get a repeat RSV vaccine. However, the question is currently being investigated.

Efficacy of Abrysvo Given During Pregnancy

Data collection is still ongoing for the Abrysvo clinical trial. However, present data show the following benefits of maternal vaccination:

• Reduced the risk of baby being hospitalized by 68% at 3 months old
• Reduced the risk of baby being hospitalized by 57% at 6 months old
• Reduced the risk of severe RSV outcomes* by 82% at 3 months old
• Reduced the risk of severe RSV outcomes* by 69% at 6 months old

You can see more details of the vaccine efficacy in the package insert. 

In the maternal vaccine trials for RSV, no infant deaths were reported due to RSV complications.** As a result, we don’t have data on whether the vaccine has any impact on reducing RSV-related mortality rates.

*Severe RSV outcomes included: low blood oxygen, need for mechanical ventilation, admission to ICU. 

**Some infant deaths occurred during clinical trials for the Abrysvo vaccine but were deemed unrelated to RSV infection or side effects of the vaccine. Infant deaths did not vary considerably between the vaccine group and the placebo group. See the package insert for more details. 

How Long Does Protection Last?

Protection is estimated to last for approximately 6 months. 

Who Should Not Get Abrysvo?

Women less than 32 weeks pregnant should not get Abrysvo as it may increase the risk of preterm birth. Those more than 36 weeks and 6 days pregnant should not get Abrysvo as there may not be time for antibodies to develop before birth. 

People with an allergy to any of the components of Abrysvo should not get the vaccine. 

Note: Clinical trials excluded people at increased risk for preterm birth and prior pregnancy complications. As a result, we don’t know for certain how results of the trials may be applied to these populations. However, the CDC doesn’t list risk for preterm birth or prior pregnancy complications as a precaution to getting Abrysvo. 

Women at high risk for preterm birth* who were excluded from the study included those with:

• BMI >40 prior to pregnancy
• IVF pregnancies
• Pre-eclampsia
• Eclampsia
• Uncontrolled gestational hypertension
• Placental abnormalities
• Polyhydramnios or oligohydramnios
• Significant bleeding or clotting disorder
• Unstable endocrine disorders (including untreated glucose intolerance & thyroid disorders)

Women with prior pregnancy complications* were eligible to be included in the study according to the investigators’ judgment, but were generally excluded. Prior pregnancy complications included:

• History of preterm (<34 weeks) birth
• Stillbirth
• Neonatal death
• Previous infant with genetic disorder or congenital anomaly

*Simply because these women were excluded from the clinical trials doesn’t necessarily mean that they should not get the RSV vaccine in pregnancy. This data is presented for your information. It is worth further discussion with a doctor about potential risks and benefits if you fall into one of the above groups. 

Who May Abrysvo Be Most Helpful For?

Abrysvo is most helpful for pregnant women who know that their infant will be at high risk for RSV exposure in the first year of life. For example, families with school or daycare aged children in the home, families with people who have public-facing jobs, etc. This is particularly true for women who know that they will not be breastfeeding their infant for the first six months of life. 

Nirsevimab is an alternative immunization strategy discussed below. Unfortunately, there have been shortages of Nirsevimab reported. If you’re considering Nirsevimab instead of Abrysvo, check with your healthcare provider about local supply.  

Note: The Canadian Pediatric Society has a preferential recommendation for Nirsevimab over Maternal RSV vaccination. Read more here: Respiratory syncytial virus (RSV) prevention strategies for the 2024-2025 viral respiratory illness season – Canadian Paediatric Society

Abrysvo Package Insert

Latest version

Previous version

Abrysvo Ingredients

Vaccine ingredients:

• RSV antigen proteins: RSV preF A and RSV preF B
• Tromethamine
• Tromethamine hydrochloride
• Sucrose
• Mannitol
• Polysorbate 80
• Sodium chloride

The RSV protein antigens contained in Abrysvo are grown in Chinese Hamster Ovary cells. The protein itself is purified before being incorporated into the vaccine, but traces of the cells may remain. 

Abrysvo: Maternal and Fetal Adverse Events

Maternal Adverse Reactions

The most commonly reported adverse reactions (≥10%) in pregnant individuals who received the Abrysvo vaccine were:

• Pain at the injection site (40.6%)
• Headache (31.0%)
• Muscle pain (26.5%)
• Nausea (20.0%)

Pregnancy Complications

In clinical trials, certain pregnancy-related conditions occurred more frequently in the vaccine group compared to the placebo group, although the differences were not statistically significant. These conditions included:

• Pre-eclampsia
• Gestational hypertension
• Preterm premature rupture of membranes (PPROM)
• Hypertension

Preterm Birth

The rate of preterm birth was higher in women who received Abrysvo compared to those in the placebo group. This wasn’t statistically significant and is still being investigated as to whether or not this is a real risk. 

Maternal and Fetal Mortality

• Maternal Deaths: One maternal death occurred in the vaccine group, caused by hemorrhage, and was deemed unrelated to the vaccine. No maternal deaths occurred in the placebo group.
• Fetal Deaths: There were 10 fetal deaths in the vaccine group and 8 in the placebo group. These deaths were attributed to various causes and were also deemed unrelated to the vaccine.

Abrysvo: Infant Adverse Events

Infant Adverse Events (Birth to 1 Month):

Adverse events were observed in:

• 37.1% of infants in the Abrysvo group
• 34.5% of infants in the placebo group

Specific Infant Conditions:

• Low birth weight: 5.1% in the Abrysvo group vs. 4.4% in the placebo group
• Neonatal jaundice: 7.2% in the Abrysvo group vs. 6.7% in the placebo group

This information is from the Abrysvo package insert. 

Post Market Research – Abrysvo

The FDA has updated safety information for Abrysvo. A study suggests a potential increased risk of Guillain-Barré syndrome (GBS), a rare condition causing muscle weakness or paralysis, within 42 days of vaccination. 

• The estimated risk is 9 extra cases of GBS per million doses of Abrysvo. 
• The evidence does not confirm a direct cause but highlights a potential link. 
• This study was in adults over 65, not pregnant women

Because these vaccines are new, we can expect more developments in post market surveillance over the coming years.  

Read more here: https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/fda-requires-guillain-barre-syndrome-gbs-warning-prescribing-information-rsv-vaccines-abrysvo-and 

About RSV Immunization After Birth With Monoclonal Antibodies (Nirsevimab & Palivizumab)

Nirsevimab and Palivizumab are both monoclonal antibodies used to prevent RSV infections in infants. Unlike vaccines, which stimulate the body to produce an immune response and memory to combat a particular infection (a process known as active immunization), monoclonal antibodies directly protect against the infection without activating the immune system (a process known as passive immunization).

The benefit of passive immunization for infants is that it doesn’t require a robust immune response from the infant’s immature immune system and it takes effect immediately rather than having a wait period while the body ramps up antibody production. 

Nirsevimab (Beyfortus) is a new and improved monoclonal antibody, while Palivizumab (Synagis) has been on the market for decades. There are some key differences between Nirsevimab (Beyfortus) and Palivizumab (Synagis), including target population, dosing, and efficacy. In general, Nirsevimab* is preferred for all infants; however, Palivizumab remains a back-up for high risk infants if Nirsevimab isn’t available. 

*Unfortunately, there have been shortages of Nirsevimab reported. If you’re considering Nirsevimab, check with your healthcare provider about local supply.  

Key Differences Between Nirsevimab & Palivizumab

Target Population

• Palivizumab: Approved primarily for high-risk infants, including preterm infants, infants with chronic lung disease, and those with congenital heart disease. It is not given to all infants due to its limited efficacy in low-risk groups and cost considerations.
• Nirsevimab: Developed as a broader protective measure against RSV, Nirsevimab is intended for all infants entering their first RSV season, including healthy term infants, preterm infants, infants with high-risk conditions, as well as high risk infants up to age 19 months entering their second RSV season (11). 

Administration and Dosing

• Palivizumab: Requires monthly injections (or every 4-6 weeks) during the RSV season (up to 5 doses), as it has a shorter half-life. The need for repeated dosing limits its use to high-risk infants due to the inconvenience and cost.
• Nirsevimab: Given as a single intramuscular injection before the RSV season. Its long half-life provides protection for the entire RSV season, making it a more convenient option for widespread prophylaxis (12).

Mechanism of Action

• Both antibodies target the RSV F (fusion) protein, but they have different binding properties.
• Nirsevimab is a newer engineered antibody with a modified Fc region to extend its half-life, allowing it to stay active longer in the infant’s body compared to Palivizumab (13).

Efficacy

• Palivizumab: Has been shown to reduce RSV hospitalizations by 56% in high-risk infants but is less effective for the general infant population. Studies show that at a two year follow up appointment, Palivizumab may reduce the RSV infection rate by 67%. Though this antibody reduces hospitalizations, it likely has little to no effect on mortality, length of hospital stay, number of days using oxygen, length of stay in intensive care unit, or mechanical ventilation days (14).  
• Nirsevimab: In clinical trials, it demonstrated around 75% efficacy in reducing RSV-associated hospitalizations in both preterm and term infants. It is considered more effective across a broader population of infants compared to Palivizumab. Nirsevimab has a yet unknown effect on mortality rate (13,15). 

Regulatory Approval

• Palivizumab has been approved and used globally for over two decades specifically for high-risk infants.
• Nirsevimab has received recent regulatory approvals, including in the U.S. (FDA approval in 2023), with a broader recommendation for use in all infants during their first RSV season.

Summary

• Palivizumab remains an option for high-risk infants needing protection but requires multiple doses, limiting its use to specific high-risk groups.
• Nirsevimab is designed for a wider range of infants, requires only a single dose, and offers longer protection for an entire RSV season, making it more practical for mass use.

FAQ: If my infant is high risk, should they get Nirsevimab or Palivizumab?

Current recommendations state that if an infant is eligible for both, they should get Nirsevimab if available. However, Palivizumab is still a secondary option if Nirsevimab is not available. Speak with your doctor about what is right for your infant. 

FAQ: Should my infant get Nirsevimab if I got the RSV vaccine during pregnancy?

In most cases, either the maternal RSV vaccine or Nirsevimab is recommended, not both. There are some exceptions — notably if you received the vaccine less than two weeks before birth, your infant may not be fully protected and Nirsevimab may be recommended. If your infant is at high risk for severe RSV, Nirsevimab may be recommended in addition to the maternal vaccine on a case-by-case basis. 

FAQ: Can my older child get Nirsevimab if they are at high risk of severe RSV?

Nirsevimab is approved for use in all infants up to 8 months of age for their first RSV reason and for high risk children up to 19 months for their second RSV season. For more information about your individual child, consult your healthcare provider. 

FAQ: Is It Safe To Get Monoclonal Antibodies At The Same Time As Vaccines?

For the past two decades, Palivizumab* has been administered alongside routine vaccinations for infants at high risk of severe RSV. Because they have differing mechanisms of action, theoretically, one shouldn’t interfere with the efficacy of the other (16). 

One minor consideration is that if an adverse event, hypersensitivity, or other allergic reaction were to occur, it would be difficult to determine whether the monoclonal antibodies or vaccine were to blame, which may make further vaccination decisions more complicated. 

*Most experts expect that Nirsevimab would behave in the body in a similar way to Palivizumab because they are similar therapies. And therefore, Nirsevimab would be alright to give alongside vaccinations because Palivizumab is. So far, the expectation that Nirsevimab and Palivizumab are similar in terms of actions and adverse events aligns with the evidence being collected in clinical trials. 

Who Would Monoclonal Antibodies Be Most Helpful For?

Monoclonal antibodies would be most helpful for infants at high risk for severe RSV infection. They may also be helpful for exclusively formula-fed infants. 

Breastfed infants without any underlying health concerns are less likely to have severe health outcomes from RSV infections; therefore, this shot would be less important for them. However, there is still potential benefit for this group, particularly given that the majority of infants hospitalized with RSV have no underlying health issues.    

Who Should Not Get Monoclonal Antibodies?

Monoclonal antibodies do not initiate an immune or inflammatory response in the same way that vaccines do; therefore, they have different precautions and side effect profiles compared to vaccines. At present, the main known risk of these monoclonal antibodies is hypersensitivity and anaphylaxis. Therefore, infants who have had an anaphylactic or hypersensitivity reaction to Nirsevimab or Palivizumab, or other human/humanized monoclonal antibodies, should not get these injections.  

Clotting disorders or thrombocytopenia are listed as cautions with any intramuscular injection including monoclonal antibodies.  

Moderate to acute respiratory infections and/or fever are a precaution to administering monoclonal antibody infections. However, they may still be given if the benefit outweighs the risk. 

Having been on the market for two decades, the side effect profile and efficacy of Palivizumab is well understood. Because Nirsevimab is so new, data is still being collected. Adverse events after Palivizumab and Nirsevimab are described below. 

Monoclonal Antibody Adverse Events

Palivizumab 

Palivizumab has been on the market much longer than Nirsevimab; therefore, we know much more about its adverse events, which is most likely why its list of adverse events is longer. 

Adverse events after Palivizumab may include:

More common:

• Bluish color of the fingernails, lips, skin, palms, or nail beds
• Blurred vision
• Confusion
• Cough
• Difficulty with breathing
• Difficulty with swallowing
• Dizziness
• Dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• Fast heartbeat
• Fever
• Hives or welts
• Irregular, fast or slow, or shallow breathing
• Itching
• Large, hive-like swelling on the face, eyelids, lips, tongue, throat, hands, legs, feet, or sex organs
• Loss of strength or energy
• Muscle pain or weakness
• Redness of the skin
• Shortness of breath
• Skin rash
• Sweating
• Tightness in the chest
• Unresponsiveness
• Unusual tiredness or weakness
• Wheezing

Incidence not known:

• Black, tarry stools
• Bleeding gums
• Blood in the urine or stools
• Pinpoint red spots on the skin
• Unusual bleeding or bruising
• Injection site reactions:
• Bleeding
• Bistering
• Burning
• Coldness
• Discoloration of the skin
• Feeling of pressure
• Injection site infection
• Inflammation
• Itching
• Lumps
• Numbness
• Pain
• Rash
• Redness
• Scarring
• Soreness
• Stinging
• Swelling
• Tenderness
• Tingling
• Ulceration
• Warmth at the injection site

The above list is from the Mayo Clinic: Palivizumab (intramuscular route)

Nirsevimab

Based on safety monitoring of >7500 infants who received Nirsevimab, the rate of adverse events was 1.3-2.0% (17). 

Adverse events may include:

Incidence not known:

• Bluish color of the fingernails, lips, or skin
• Chest tightness
• Cough
• Difficulty swallowing
• Dizziness
• Fast heartbeat
• Hives, itching, skin rash
• Muscle weakness
• Puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• Unusual tiredness or weakness

*Anaphylaxis is a theoretical concern with Nirsevimab but hasn’t been reported.

Nirsevimab is relatively new and all adverse events have likely not yet come to light. 

The above list is from the Mayo Clinic: Nirsevimab-alip (intramuscular route)

Monoclonal Antibody Package Inserts

Palivizumab: Synagis

Nirsevimab: Beyfortus

Synagis Ingredients (Palivizumab)

Monoclonal antibody injection contains:

• Palivizumab
• Chloride
• Glycine
• Histidine
• Water

Palivizumab is an immunoblogbulin G1 kappa protein that is made up of both human (95%) and mouse (5%) antibody sequences. Palivizumab is produced by recombinant DNA technology in a mammalian cell (NSO) suspension culture and then purified. NSO is a cell line from murine myeloma. 

Beyfortus Ingredients (Nirsevimab)

Monoclonal antibody injection contains:

• Nirsevimab-alip
• Arginine hydrochloride
• Histidine
• L-histidine hydrochloride monohydrate
• Polysorbate 80
• Sucrose
• Water

Nirsevimab-alip is a human immunoglobulin G1 kappa (IgG1K), specifically an RSV F protein-directed fusion inhibitor. It is produced in Chinese hamster ovary cells by recombinant DNA technology then purified. 

Controversy & Confusion

It seems as though all immunizations come with some degree of controversy. The following are some of the issues that you may hear discussed in terms of RSV vaccines and RSV monoclonal antibody immunizations:

1. Language around Beyfortus (Nirsevimab) when it was first introduced made it sound like a vaccine; in actuality, it is a monoclonal antibody, and there are some key differences.
2. The first attempted RSV vaccine in the 1960s caused more harm than benefit.
3. RSV vaccine may increase risk of preterm birth.
4. Some pregnant women are administered the wrong RSV vaccine.

1. Beyfortus is not a Vaccine

Beyfortus (Nirsevimab) is not a vaccine, but when it was rolled out, it was called an “immunization.” This understandably confused a lot of parents because typically the terms “immunization” and “vaccination” are used interchangeably. Additionally, Beyfortus is given as an intramuscular injection and is used to protect against a common childhood illness – more factors that are typically associated with vaccines, which understandably added to the confusion. 

The bottom line is that Beyfortus is an immunization, but it is not a vaccine. 

Some important terms to know:

Immunization: The process of becoming immune to an infection. A person may become immune via vaccination, injection with monoclonal antibodies, natural infection, or transplacental transfer of antibodies. In general, immunization typically refers to vaccination, though it is also correct to use this term to describe the protection acquired with monoclonal antibodies. 

Vaccination: The process of receiving a vaccine. If the vaccine works to stimulate an adequate antibody response, then immunization has occurred. 

Passive Immunization: Immunity is given without the body needing to mount an immune response. Monoclonal antibodies are a form of passive immunization as is transplacental transfer of maternal antibodies. 

Active Immunization: Immunity that develops as a result of the body’s own production of protective antibodies. Vaccination is a form of active immunization. 

Read more: How headlines about the RSV antibody injection could cloud parents’ decision-making

2. Original RSV Vaccine Caused More Harm Than Benefit

In the 1960s, an RSV vaccine was attempted. It failed miserably in clinical trials: 80% of the children given the vaccine were hospitalized with severe respiratory disease and two died (18).

Decades of research followed this tragedy, and scientists have a good grasp on why the original vaccine failed and how to avoid history repeating itself. The vaccines on the market now are protein subunit vaccines, which are very different from the formalin-inactivated vaccines that caused the respiratory problems in the 1960s. Clinical trials show vastly different outcomes and currently approved vaccines are much safer and more effective than the failed RSV vaccine from the 1960s. 

3. Maternal RSV Vaccine May Increase Risk of Preterm Birth

Before Abrysvo was licensed, another pharmaceutical company was attempting to develop a similar RSV vaccine and had to abandon it during clinical trials because of an unacceptable increase in premature births (19). In Abrysvo clinical trials, more women in the vaccine group delivered babies prematurely compared to the placebo group; however, this number was not significantly different enough to draw a conclusion that the vaccine was causing this increase in premature births. The package insert refers to this as a “numerical imbalance.”

To reduce the risk and potential harm of premature births following RSV vaccination, Abrysvo was only licensed to be given between 32-36 weeks of gestation. The rate of premature births following maternal RSV vaccination is being watched in post-marketing studies. See this page for more information: Abrysvo – FDA

The first post-marketing study that we found reported that there was a statistically significant increase in the rate of preterm births among women who got the RSV vaccine at the end of their pregnancy: Safety of RSV Vaccine among Pregnant Individuals: A Real-World Pharmacovigilance Study Using Vaccine Adverse Event Reporting System.

4. RSV Vaccine Administration Errors

There are currently two RSV vaccines available in the USA. 

1.  Abrysvo (formulated without adjuvants) is approved for pregnant women. 
2.  Arexvy (formulated with adjuvants) is NOT approved for pregnant women. 

There have been reports of pregnant individuals being vaccinated with the wrong RSV vaccine by mistake. If you choose to be vaccinated during pregnancy, ensure that your doctor has Abrysvo and not Arexvy. 

There have also been reports of Abrysvo being inappropriately administered prior to 32 weeks of pregnancy and to infants. 

Read more about vaccine administration errors here: 

• Information on Respiratory Syncytial Virus (RSV) Vaccine Administration Errors in Young Children and Pregnant People
• RSV vaccines administered in error to infants and pregnant people, CDC reports | The BMJ 

Bottom Line – RSV Immunization

RSV is the leading cause of hospitalization in infants under a year old in the United States. There are two different options for protecting your infant via immunization:

1. Maternal vaccination with Abrysvo
2. Infant monoclonal antibody infection with Nirsevimab/Beyfortus (or less likely with Palivizumab/Synagis)

Both of these options are shown to reduce the risk of hospitalization and severe RSV outcomes. At this point, neither have been shown to have an impact on mortality.  

During pregnancy, you will likely be offered vaccination between 32-36 weeks with Abrysvo – an RSV vaccine. If given at least two weeks before birth, your body will produce antibodies that are passed to your baby through the placenta that will reduce your baby’s risk of hospitalization due to RSV. In our opinion there is a real possibility that this vaccine can increase the risk of preterm birth. 

An alternative to RSV vaccination during pregnancy is passive immunization with a monoclonal antibody injection (Nirsevimab/Beyfortus). Based on what we know so far, we believe that the antibody injection may have a slightly more favorable side effect and efficacy profile as compared with the maternal vaccine. However, both the maternal vaccine (Abrysvo) and the monoclonal antibody therapy (Nirsevimab) are quite new; we can expect more information on both efficacy and side effects to be clarified in the coming years. 

If you choose immunization by either maternal vaccine or monoclonal antibody injection, remember that protection is not 100% and precautions like hand-washing, avoiding exposing infants to public places, reducing people in close contact with your infant, etc. still need to be in place regardless of immunization status. Breastfeeding is also protective against RSV infection but may not be as effective as immunization. 

References:

1. US Centers for Disease Control and Prevention. (24 Aug. 2024). Respiratory Syncytial Virus Infection (RSV). Cdc.gov. https://www.cdc.gov/rsv/index.html
2. Hall, C. B., Douglas, R. G., Jr, & Geiman, J. M. (1980). Possible transmission by fomites of respiratory syncytial virus. The Journal of infectious diseases, 141(1), 98–102. https://doi.org/10.1093/infdis/141.1.98
3. Jain, H., Schweitzer, J. W., & Justice N. A. Respiratory Syncytial Virus Infection in Children. [Updated 2023 Jun 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; Available from: https://www.ncbi.nlm.nih.gov/books/NBK459215/
4. Curns, A. T., Rha, B., Lively, J. Y., Sahni, L. C., Englund, J. A., Weinberg, G. A., Halasa, N. B., Staat, M. A., Selvarangan, R., Michaels, M., Moline, H., Zhou, Y., Perez, A., Rohlfs, C., Hickey, R., Lacombe, K., McHenry, R., Whitaker, B., Schuster, J., Pulido, C. G., Strelitz, B., Quigley, C., Weddle DNP, G., Avadhanula, V., Harrison, C. J., Stewart, L. S., Schlaudecker, E., Szilagyi, P. G., Klein, E. J., Boom, J., Williams, J. V., Langley, G., Gerber, S. I., Hall, A. J., McMorrow, M. L. (2024). Respiratory Syncytial Virus-Associated Hospitalizations Among Children <5 Years Old: 2016 to 2020. Pediatrics March 2024; 153 (3): e2023062574. 10.1542/peds.2023-062574
5. US Centers for Disease Control and Prevention. (5 Sep. 2023). Increased Respiratory Syncytial Virus (RSV) Activity in Parts of the Southeastern United States: New Prevention Tools Available to Protect Patients. Cdc.gov. https://emergency.cdc.gov/han/2023/han00498.asp
6. Suh, M., Movva, N., Jiang, X., Bylsma, L. C., Reichert, H., Fryzek, J. P., & Nelson, C. B. (2022). Respiratory Syncytial Virus Is the Leading Cause of United States Infant Hospitalizations, 2009-2019: A Study of the National (Nationwide) Inpatient Sample. The Journal of infectious diseases, 226(Suppl 2), S154–S163. https://doi.org/10.1093/infdis/jiac120
7. Byington, C. L., Wilkes, J., Korgenski, K., & Sheng, X. (2015). Respiratory syncytial virus-associated mortality in hospitalized infants and young children. Pediatrics, 135(1), e24–e31. https://doi.org/10.1542/peds.2014-2151
8. Munro, A. P. S., Martinón-Torres, F., Drysdale, S. B., & Faust, S. N. (2023). The disease burden of respiratory syncytial virus in Infants. Current opinion in infectious diseases, 36(5), 379–384. https://doi.org/10.1097/QCO.0000000000000952
9. Mineva, G. M., Purtill, H., Dunne, C. P., & Philip, R. K. (2023). Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention. BMJ global health, 8(2), e009693. https://doi.org/10.1136/bmjgh-2022-009693
10. National Institute of Child Health and Human Development. (2024). Respiratory Syncytial Virus Vaccine. Drugs and Lactation Database (LactMed®). 
11. Jones, J. M., Fleming-Dutra, K. E., Prill, M. M., et al. (25 Aug 2023). Use of Nirsevimab for the Prevention of Respiratory Syncytial Virus Disease Among Infants and Young Children: Recommendations of the Advisory Committee on Immunization Practices — United States. MMWR Morb Mortal Wkly Rep 2023;72:920–925. DOI: http://dx.doi.org/10.15585/mmwr.mm7234a4
12. American Academy of Pediatrics. (2024). Red Book: 2024–2027 Report of the Committee on Infectious Diseases: AAP Recommendations for the Prevention of RSV Disease in Infants and Children. https://publications.aap.org/redbook/resources/25379/AAP-Recommendations-for-the-Prevention-of-RSV
13. Hammitt, L. L., Dagan, R., Yuan, Y., Baca Cots, M., Bosheva, M., Madhi, S. A., & Villafana, T. (2022). Nirsevimab for prevention of RSV in healthy late-preterm and term infants. New England Journal of Medicine, 386(9), 837-846.
14. Garegnani, L., Styrmisdóttir, L., Roson Rodriguez, P., Escobar Liquitay, C. M., Esteban, I., & Franco, J. V. (2021). Palivizumab for preventing severe respiratory syncytial virus (RSV) infection in children. The Cochrane database of systematic reviews, 11(11), CD013757. https://doi.org/10.1002/14651858.CD013757.pub2
15. Sullivan, K., & Sullivan, B. (2024). Does Nirsevimab prevent lower respiratory infections caused by respiratory syncytial virus?. J Perinatol 44, 767–769. https://doi.org/10.1038/s41372-024-01970-y
16. Esposito, S., Abu-Raya, B., Bonanni, P., Cahn-Sellem, F., Flanagan, K. L., Martinon Torres, F., Mejias, A., Nadel, S., Safadi, M. A. P., & Simon, A. (2021). Coadministration of Anti-Viral Monoclonal Antibodies With Routine Pediatric Vaccines and Implications for Nirsevimab Use: A White Paper. Frontiers in immunology, 12, 708939. https://doi.org/10.3389/fimmu.2021.708939
17. Abu-Raya, B., Langley, J. M., Lavoie, P. (2024). Nirsevimab to reduce infant morbidity from respiratory syncytial virus. CMAJ Oct, 196 (32) E1114-E1117; DOI: 10.1503/cmaj.240780
18. Derscheid, R. J., Gallup, J. M., Knudson, C. J., Varga, S. M., Grosz, D. D., van Geelen, A., Hostetter, S. J., & Ackermann, M. R. (2013). Effects of formalin-inactivated respiratory syncytial virus (FI-RSV) in the perinatal lamb model of RSV. PloS one, 8(12), e81472. https://doi.org/10.1371/journal.pone.0081472
19. Boytchev H. (2023). Maternal RSV vaccine: Further analysis is urged on preterm births. BMJ; 381 :p1021 doi:10.1136/bmj.p1021

Resources

We have resources that go deeper into all things vaccines to help you make informed choices for your family. Check out our popular Vaccine Strategy Guide. 

For further information, you may find these links helpful:

• CDC RSV information
• Statement on the prevention of respiratory syncytial virus disease in infants – Canada.ca
• Abrysvo (Maternal RSV Vaccine) package insert
• Abrysvo Monograph
• Abrysvo FDA approval letter
• Beyfortus/Nirsevimab (Infant Monoclonal Antibodies) package insert
• Beyfortus Monograph
• Beyfortus/Nirsevimab FDA approval letter
• Synagis/Palivizumab (High Risk Infant Monoclonal Antibodies) package insert
• Synagis monograph
• Synagis first FDA approval letter 

Additional Studies/Reviews & Background Information

About RSV

Jain, H., Schweitzer, J. W., Justice, N. A. Respiratory Syncytial Virus Infection in Children. [Updated 2023 Jun 20]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459215/

Byington, C. L., Wilkes, J., Korgenski, K., & Sheng, X. (1 Jan 2015). Respiratory syncytial virus-associated mortality in hospitalized infants and young children. American Academy of Pediatrics. Pediatrics, 135(1), e24–e31. https://doi.org/10.1542/peds.2014-2151

Bergeron, H. C., & Tripp, R. A. (2021). Immunopathology of RSV: An Updated Review. Viruses, 13(12), 2478. https://doi.org/10.3390/v13122478

Langedijk, A. C., Harding, E. R., Konya, B., Vrancken, B., Lebbink, R. J., Evers, A., Willemsen, J., Lemey, P., & Bont, L. J. (2022). A systematic review on global RSV genetic data: Identification of knowledge gaps. Reviews in medical virology, 32(3), e2284. https://doi.org/10.1002/rmv.2284

Suh, M., Movva, N., Jiang, X., Bylsma, L. C., Reichert, H., Fryzek, J. P., & Nelson, C. B. (2022). Respiratory Syncytial Virus Is the Leading Cause of United States Infant Hospitalizations, 2009-2019: A Study of the National (Nationwide) Inpatient Sample. The Journal of infectious diseases, 226(Suppl 2), S154–S163. https://doi.org/10.1093/infdis/jiac120

Meier, K., Riepl, A., Voitl, P., Lischka, L., Voitl, J. J. M., Langer, K., Kuzio, U., Redlberger-Fritz, M., & Diesner-Treiber, S. C. (2024). Characterisation of RSV infections in children without chronic diseases aged 0-36 months during the post-COVID-19 winter season 2022/2023. Frontiers in pediatrics, 12, 1342399. https://doi.org/10.3389/fped.2024.1342399 

Shi, T., Balsells, E., Wastnedge, E., Singleton, R., Rasmussen, Z. A., Zar, H. J., Rath, B. A., Madhi, S. A., Campbell, S., Vaccari, L. C., Bulkow, L. R., Thomas, E. D., Barnett, W., Hoppe, C., Campbell, H., & Nair, H. (2015). Risk factors for respiratory syncytial virus associated with acute lower respiratory infection in children under five years: Systematic review and meta-analysis. Journal of global health, 5(2), 020416. https://doi.org/10.7189/jogh.05.020416 

Munro, A. P. S., Martinón-Torres, F., Drysdale, S. B., & Faust, S. N. (2023). The disease burden of respiratory syncytial virus in Infants. Current opinion in infectious diseases, 36(5), 379–384. https://doi.org/10.1097/QCO.0000000000000952

Guare, E. G., Zhao, R., Ssentongo, P., Batra, E. K., Chinchilli, V. M., & Paules, C. I. (2024). Rates of Sudden Unexpected Infant Death Before and During the COVID-19 Pandemic. JAMA Netw Open. 2024;7(9):e2435722. doi:10.1001/jamanetworkopen.2024.35722

Curns, A. T., Rha, B., Lively, J. Y., Sahni, L. C., Englund, J. A., Weinberg, G. A., Halasa, N. B., Staat, M. A., Selvarangan, R., Michaels, M., Moline, H., Zhou, Y., Perez, A., Rohlfs, C., Hickey, R., Lacombe, K., McHenry, R., Whitaker, B., Schuster, J., Pulido, C. G., Strelitz, B., Quigley, C., Weddle DNP, G., Avadhanula, V., Harrison, C. J., Stewart, L. S., Schlaudecker, E., Szilagyi, P. G., Klein, E. J., Boom, J., Williams, J. V., Langley, G., Gerber, S. I., Hall, A. J., McMorrow, M. L. (2024). Respiratory Syncytial Virus-Associated Hospitalizations Among Children <5 Years Old: 2016 to 2020. Pediatrics March 2024; 153 (3): e2023062574. 10.1542/peds.2023-062574

Mineva, G. M., Purtill, H., Dunne, C. P., & Philip, R. K. (2023). Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention. BMJ global health, 8(2), e009693. https://doi.org/10.1136/bmjgh-2022-009693

Wheeler, S. M., Dotters-Katz, S., Heine, R. P., Grotegut, C. A., & Swamy, G. K. (2015). Maternal Effects of Respiratory Syncytial Virus Infection during Pregnancy. Emerging infectious diseases, 21(11), 1951–1955. https://doi.org/10.3201/eid2111.150497

Norlander, A. E., & Peebles, R. S., Jr. (2020). Innate Type 2 Responses to Respiratory Syncytial Virus Infection. Viruses, 12(5), 521. https://doi.org/10.3390/v12050521

Manti, S., Leonardi, S., Rezaee, F., Harford, T. J., Perez, M. K., & Piedimonte, G. (2022). Effects of Vertical Transmission of Respiratory Viruses to the Offspring. Frontiers in immunology, 13, 853009. https://doi.org/10.3389/fimmu.2022.853009

Swets, M. C., Russell, C. D., Harrison, E. M., Docherty, A. B., Lone, N., Girvan, M., Hardwick, H. E., ISARIC4C Investigators, Visser, L. G., Openshaw, P. J. M., Groeneveld, G. H., Semple, M. G., & Baillie, J. K. (2022). SARS-CoV-2 co-infection with influenza viruses, respiratory syncytial virus, or adenoviruses. Lancet (London, England), 399(10334), 1463–1464. https://doi.org/10.1016/S0140-6736(22)00383-X

Le-Corre, N., Pérez, R., Vizcaya, C., Martínez-Valdebenito, C., López, T., Monge, M., Alarcón, R., Moller, F., Martínez, M. T., Massardo, J. M., & Ferrés, M. (2021). Relevance of codetection of respiratory viruses in the severity of acute respiratory infection in hospitalized children. Relevancia de la co-detección de virus respiratorios en la severidad de la infección respiratoria aguda en niños hospitalizados. Andes pediatrica : revista Chilena de pediatria, 92(3), 349–358. https://doi.org/10.32641/andespediatr.v92i3.1756

Esposito, S., Abu Raya, B., Baraldi, E., Flanagan, K., Martinon Torres, F., Tsolia, M., & Zielen, S. (2022). RSV Prevention in All Infants: Which Is the Most Preferable Strategy?. Frontiers in immunology, 13, 880368. https://doi.org/10.3389/fimmu.2022.880368

Young, M., & Smitherman, L. (2021). Socioeconomic Impact of RSV Hospitalization. Infectious diseases and therapy, 10(Suppl 1), 35–45. https://doi.org/10.1007/s40121-020-00390-7

Wrotek, A., Wrotek, O., & Jackowska, T. (2023). The Impact of RSV Hospitalization on Children’s Quality of Life. Diseases (Basel, Switzerland), 11(3), 111. https://doi.org/10.3390/diseases11030111

Wrotek, A., Wrotek, O., & Jackowska, T. (2023). The Estimate of Parental Quality of Life Loss Due to Respiratory Syncytial Virus (RSV) Hospitalization. Diseases (Basel, Switzerland), 11(4), 126. https://doi.org/10.3390/diseases11040126

Trautmannsberger, I., Plagg, B., Adamek, I., Mader, S., de Luca, D., Esposito, S., Silfverdal, S. A., Zimmermann, L. J. I., Tischer, C., & ResQ Family study group (2024). The Multifaceted Burden of Respiratory Syncytial Virus (RSV) Infections in Young Children on the Family: A European Study. Infectious diseases and therapy, 13(7), 1531–1573. https://doi.org/10.1007/s40121-024-00989-0 

About RSV Vaccines

Kulkarni, P. S., Hurwitz, J. L., Simões, E. A. F., & Piedra, P. A. (2018). Establishing Correlates of Protection for Vaccine Development: Considerations for the Respiratory Syncytial Virus Vaccine Field. Viral immunology, 31(2), 195–203. https://doi.org/10.1089/vim.2017.0147

Jorquera, P. A., Anderson, L., & Tripp, R. A. (2016). Understanding respiratory syncytial virus (RSV) vaccine development and aspects of disease pathogenesis. Expert review of vaccines, 15(2), 173–187. https://doi.org/10.1586/14760584.2016.1115353

Chu, K. B., & Quan, F. S. (2023). Respiratory Viruses and Virus-like Particle Vaccine Development: How Far Have We Advanced?. Viruses, 15(2), 392. https://doi.org/10.3390/v15020392

About Abrysvo RSV Vaccine

US Centers for Disease Control and Prevention. (30 Aug 2024). RSV Vaccine Guidance for Pregnant People. Cdc.gov. https://www.cdc.gov/rsv/hcp/vaccine-clinical-guidance/pregnant-people.html

Respiratory Syncytial Virus Vaccine. (2024). In Drugs and Lactation Database (LactMed®). National Institute of Child Health and Human Development.

Boytchev, H. (2023). Maternal RSV vaccine: Further analysis is urged on preterm births. BMJ 2023; 381 :p1021 doi:10.1136/bmj.p1021. https://www.bmj.com/content/381/bmj.p1021/rapid-responses

Boytchev, H. (2023). FDA advisers back Pfizer’s maternal RSV vaccine after voicing safety concerns. BMJ 2023; 381 :p1187 doi:10.1136/bmj.p1187 https://www.bmj.com/content/381/bmj.p1187

Boytchev, H. (2023). Concerns over informed consent for pregnant women in Pfizer’s RSV vaccine trial. BMJ 2023; 383 :p2620 doi:10.1136/bmj.p2620 https://www.bmj.com/content/383/bmj.p2620

Boytchev, H. (2024). RSV vaccines administered in error to infants and pregnant people, CDC reports. BMJ 2024; 384 :q236 doi:10.1136/bmj.q236 https://www.bmj.com/content/384/bmj.q236

Alami, A., Perez-Lloret, S., Mattison, D. R. (2024). Safety of RSV Vaccine among Pregnant Individuals: A Real-World Pharmacovigilance Study Using Vaccine Adverse Event Reporting System. medRxiv 2024.04.19.24306090; doi:https://doi.org/10.1101/2024.04.19.24306090

About RSV Immunization Options

US Centers for Disease Control and Prevention. (30 Aug 2024). Respiratory Syncytial Virus Infection: Immunizations to Protect Infants. Cdc.gov. https://www.cdc.gov/rsv/vaccines/protect-infants.html

Jeannette L. Comeau MD MSc, Dorothy L. Moore MD, Michelle A. Barton MD. (6 Nov 2024). Respiratory syncytial virus (RSV) prevention strategies for the 2024-2025 viral respiratory illness season. Canadian Paediatric Society, Infectious Diseases and Immunization Committee. Cps.ca. https://cps.ca/en/documents/position/rsv-prevention-2024-2025

US Centers for Disease Control and Prevention. (4 Sep 2024). RSV (Respiratory Syncytial Virus) Immunizations. Cdc.gov. https://www.cdc.gov/vaccines/vpd/rsv/index.html

American Academy of Pediatrics. (21 Feb 2024). AAP Recommendations for the Prevention of RSV Disease in Infants and Children. Red Book Online. Publications. AAP.org. https://publications.aap.org/redbook/resources/25379/AAP-Recommendations-for-the-Prevention-of-RSV

Public Health Agency of Canada. (9 Aug 2024). Respiratory syncytial virus (RSV) vaccines: Canadian Immunization Guide. Canada.ca. https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/respiratory-syncytial-virus.html

Robinson, J. L., & Papenburg, J. (2023). The rapidly changing landscape of respiratory syncytial virus prophylaxis. Journal of the Association of Medical Microbiology and Infectious Disease Canada, 8(3), 165–171. https://doi.org/10.3138/jammi-2023-05-31

About Nirsevimab

Jones, J. M., Fleming-Dutra, K. E., Prill, M. M., et al. (2023). Use of Nirsevimab for the Prevention of Respiratory Syncytial Virus Disease Among Infants and Young Children: Recommendations of the Advisory Committee on Immunization Practices — United States. MMWR Morb Mortal Wkly Rep 2023;72:920–925. DOI: http://dx.doi.org/10.15585/mmwr.mm7234a4

US Centers for Disease Control and Prevention. (28 Sep 2023). Healthcare Providers: RSV Immunization for Infants and Young Children. Cdc.gov. https://www.cdc.gov/vaccines/vpd/rsv/hcp/child.html

US Food & Drug Administration. (17 Jul 2023). FDA Approves New Drug to Prevent RSV in Babies and Toddlers. FDA.gov. https://www.fda.gov/news-events/press-announcements/fda-approves-new-drug-prevent-rsv-babies-and-toddlers

US Food & Drug Administration. (17 Jul 2023). Drug Trials Snapshots: BEYFORTUS. FDA.gov. https://www.fda.gov/drugs/drug-approvals-and-databases/drug-trials-snapshots-beyfortus

US Food & Drug Administration. (8 Jun 2023). FDA Briefing Document – Nirsevimab. Antimicrobial Drugs Advisory Committee Meeting. https://www.fda.gov/media/169226/download

Mayo Clinic. (31 Jan 2024). Nirsevimab-alip (intramuscular route). Mayoclinic.org. https://www.mayoclinic.org/drugs-supplements/nirsevimab-alip-intramuscular-route/description/drg-20552487

American Academy of Pediatrics. (8 Nov 2024). Nirsevimab Frequently Asked Questions. AAP.org. https://www.aap.org/en/patient-care/respiratory-syncytial-virus-rsv-prevention/nirsevimab-frequently-asked-questions/

Esposito, S., Abu-Raya, B., Bonanni, P., Cahn-Sellem, F., Flanagan, K. L., Martinon Torres, F., Mejias, A., Nadel, S., Safadi, M. A. P., & Simon, A. (2021). Coadministration of Anti-Viral Monoclonal Antibodies With Routine Pediatric Vaccines and Implications for Nirsevimab Use: A White Paper. Frontiers in immunology, 12, 708939. https://doi.org/10.3389/fimmu.2021.708939 

Sullivan, K., Sullivan, B. (2024). Does Nirsevimab prevent lower respiratory infections caused by respiratory syncytial virus?. J Perinatol 44, 767–769. https://doi.org/10.1038/s41372-024-01970-y 

Hammitt, L. L., Dagan, R., Yuan, Y., Baca Cots, M., Bosheva, M., Madhi, S. A., Muller, W. J., Zar, H. J., Brooks, D., Grenham, A., Wählby Hamrén, U., Mankad, V. S., Ren, P., Takas, T., Abram, M. E., Leach, A., Griffin, M. P., Villafana, T., & MELODY Study Group (2022). Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants. The New England journal of medicine, 386(9), 837–846. https://doi.org/10.1056/NEJMoa2110275

Sullivan, K., Sullivan, B. (2024). Does Nirsevimab prevent lower respiratory infections caused by respiratory syncytial virus?. J Perinatol 44, 767–769. https://doi.org/10.1038/s41372-024-01970-y

Riccò, M., Cascio, A., Corrado, S., Bottazzoli, M., Marchesi, F., Gili, R., Giuri, P. G., Gori, D., & Manzoni, P. (2024). Impact of Nirsevimab Immunization on Pediatric Hospitalization Rates: A Systematic Review and Meta-Analysis (2024). Vaccines, 12(6), 640. https://doi.org/10.3390/vaccines12060640 

Robinson, J. L., & Papenburg, J. (2023). The rapidly changing landscape of respiratory syncytial virus prophylaxis. Journal of the Association of Medical Microbiology and Infectious Disease Canada, 8(3), 165–171. https://doi.org/10.3138/jammi-2023-05-31

Hammitt, L. L., Dagan, R., Yuan, Y., Baca Cots, M., Bosheva, M., Madhi, S. A., Muller, W. J., Zar, H. J., Brooks, D., Grenham, A., Wählby Hamrén, U., Mankad, V. S., Ren, P., Takas, T., Abram, M. E., Leach, A., Griffin, M. P., Villafana, T., & MELODY Study Group (2022). Nirsevimab for Prevention of RSV in Healthy Late-Preterm and Term Infants. The New England journal of medicine, 386(9), 837–846. https://doi.org/10.1056/NEJMoa2110275

Abu-Raya, B., Langley, J. M., & Lavoie, P. (2024). Nirsevimab to reduce infant morbidity from respiratory syncytial virus. CMAJ Oct, 196 (32) E1114-E1117; DOI: 10.1503/cmaj.240780

Wilkins, D., Wählby Hamrén, U., Chang, Y., Clegg, L. E., Domachowske, J., Englund, J. A., Muller, W. J., Leach, A., Kelly, E. J., & Villafana, T. (2024). RSV Neutralizing Antibodies Following Nirsevimab and Palivizumab Dosing. Pediatrics, 154(5), e2024067174. https://doi.org/10.1542/peds.2024-067174

Simões, E. A. F., Madhi, S. A., Muller, W. J., Atanasova, V., Bosheva, M., Cabañas, F., Baca Cots, M., Domachowske, J. B., Garcia-Garcia, M. L., Grantina, I., Nguyen, K. A., Zar, H. J., Berglind, A., Cummings, C., Griffin, M. P., Takas, T., Yuan, Y., Wählby Hamrén, U., Leach, A., & Villafana, T. (2023). Efficacy of nirsevimab against respiratory syncytial virus lower respiratory tract infections in preterm and term infants, and pharmacokinetic extrapolation to infants with congenital heart disease and chronic lung disease: a pooled analysis of randomised controlled trials. The Lancet. Child & adolescent health, 7(3), 180–189. https://doi.org/10.1016/S2352-4642(22)00321-2

Tuffy, K. M., Ahani, B., Domachowske, J. B., Furuno, K., Ji, H., Madhi, S. A., Mankad, V. S., Hamrén, U. W., Villafana, T., Wang, Y., Kelly, E. J., & Wilkins, D. (2024). Molecular and phenotypic characteristics of respiratory syncytial virus isolates recovered from medically vulnerable children: An exploratory analysis of a phase 2/3 randomized, double-blind, palivizumab-controlled trial of nirsevimab (MEDLEY). Vaccine, 42(24), 126276. https://doi.org/10.1016/j.vaccine.2024.126276

Turalde-Mapili, M. W. R., Mapili, J. A. L., Turalde, C. W. R., & Pagcatipunan, M. R. (2023). The efficacy and safety of nirsevimab for the prevention of RSV infection among infants: A systematic review and meta-analysis. Frontiers in pediatrics, 11, 1132740. https://doi.org/10.3389/fped.2023.1132740

About Palivizumab

American Academy of Pediatrics – Committee on Infectious Diseases. (26 Jun 2023). Palivizumab Prophylaxis in Infants and Young Children at Increased Risk of Hospitalization for Respiratory Syncytial Virus Infection. Pediatrics; 152 (1): e2023061803. https://doi.org/10.1542/peds.2023-061803

Garegnani, L., Styrmisdóttir, L., Roson Rodriguez, P., Escobar Liquitay, C.M., Esteban, I., Franco, J. V. A. (16 Nov 2021). Palivizumab for preventing severe respiratory syncytial virus (RSV) infection in children. Cochrane Database of Systematic Reviews 2021, Issue 11. Art. No.: CD013757. DOI: 10.1002/14651858.CD013757.pub2. https://www.cochrane.org/CD013757/ARI_palivizumab-respiratory-syncytial-virus-infection-prevention-children

Garegnani, L., Styrmisdóttir, L., Roson Rodriguez, P., Escobar Liquitay, C. M., Esteban, I., & Franco, J. V. (2021). Palivizumab for preventing severe respiratory syncytial virus (RSV) infection in children. The Cochrane database of systematic reviews, 11(11), CD013757. https://doi.org/10.1002/14651858.CD013757.pub2

Resch B. (2017). Product review on the monoclonal antibody palivizumab for prevention of respiratory syncytial virus infection. Human vaccines & immunotherapeutics, 13(9), 2138–2149. https://doi.org/10.1080/21645515.2017.1337614

Makari, D., Checchia, P. A., & Devincenzo, J. (2014). Rationale for full-season dosing for passive antibody prophylaxis of respiratory syncytial virus. Human vaccines & immunotherapeutics, 10(3), 607–614. https://doi.org/10.4161/hv.27426

Claydon, J., Sur, A., Callejas, A., Ladd, M., Kwan, E., Taylor, R., Turvey, S. E., Solimano, A., Lavoie, P. M., & Marr, N. (2017). Respiratory syncytial virus-neutralizing serum antibody titers in infants following palivizumab prophylaxis with an abbreviated dosing regimen. PloS one, 12(4), e0176152. https://doi.org/10.1371/journal.pone.0176152

Kim, D., Saleem, M., Paes, B., Mitchell, I., & Lanctôt, K. L. (2019). Respiratory Syncytial Virus Prophylaxis in Infants With Congenital Diaphragmatic Hernia in the Canadian Respiratory Syncytial Virus Evaluation Study of Palivizumab, 2005-2017. Clinical infectious diseases : an official publication of the Infectious Diseases Society of America, 69(6), 980–986. https://doi.org/10.1093/cid/ciy1010

Paes, B., Kim, D., Saleem, M., Wong, S., Mitchell, I., Lanctot, K. L., & and the CARESS investigators (2019). Respiratory syncytial virus prophylaxis in infants with congenital airway anomalies compared to standard indications and complex medical disorders. European journal of pediatrics, 178(3), 377–385. https://doi.org/10.1007/s00431-018-03308-1

Wang, D. Y., Saleem, M., Paes, B. A., Mitchell, I., Li, A., Lanctôt, K. L., & CARESS Investigators (2019). Respiratory Syncytial Virus Prophylaxis in Neurologic and Muscular Disorders in the Canadian Respiratory Syncytial Virus Evaluation Study of Palivizumab. The Pediatric infectious disease journal, 38(8), 775–780. https://doi.org/10.1097/INF.0000000000002297

Paes, B., Saleem, M., Kim, D., Lanctôt, K. L., & Mitchell, I. (2019). Respiratory illness and respiratory syncytial virus hospitalization in infants with a tracheostomy following prophylaxis with palivizumab. European journal of clinical microbiology & infectious diseases : official publication of the European Society of Clinical Microbiology, 38(8), 1561–1568. https://doi.org/10.1007/s10096-019-03588-x

Claydon, J., Popescu, C. R., Shaiba, L., Christopherson, C., Human, D., Taylor, R., Solimano, A., & Lavoie, P. M. (2019). Outcomes related to respiratory syncytial virus with an abbreviated palivizumab regimen in children with congenital heart disease: a descriptive analysis. CMAJ open, 7(1), E88–E93. https://doi.org/10.9778/cmajo.20180167

O’Hagan, S., Galway, N., Shields, M. D., Mallett, P., & Groves, H. E. (2023). Review of the Safety, Efficacy and Tolerability of Palivizumab in the Prevention of Severe Respiratory Syncytial Virus (RSV) Disease. Drug, healthcare and patient safety, 15, 103–112. https://doi.org/10.2147/DHPS.S348727

Checchia, P. A., Nalysnyk, L., Fernandes, A. W., Mahadevia, P. J., Xu, Y., Fahrbach, K., & Welliver, R. C., Sr (2011). Mortality and morbidity among infants at high risk for severe respiratory syncytial virus infection receiving prophylaxis with palivizumab: a systematic literature review and meta-analysis. Pediatric critical care medicine : a journal of the Society of Critical Care Medicine and the World Federation of Pediatric Intensive and Critical Care Societies, 12(5), 580–588. https://doi.org/10.1097/PCC.0b013e3182070990

Mohan, A. K., Braun, M. M., Ellenberg, S., Hedje, J., & Coté, T. R. (2004). Deaths among children less than two years of age receiving palivizumab: an analysis of comorbidities. The Pediatric infectious disease journal, 23(4), 342–345. https://doi.org/10.1097/00006454-200404000-00013

Sanders, S. L., Agwan, S., Hassan, M., Bont, L. J., & Venekamp, R. P. (2023). Immunoglobulin treatment for hospitalised infants and young children with respiratory syncytial virus infection. The Cochrane database of systematic reviews, 10(10), CD009417. https://doi.org/10.1002/14651858.CD009417.pub3

Protective Effect Of Breastfeeding On RSV Outcomes

Mineva, G. M., Purtill, H., Dunne, C. P., & Philip, R. K. (2023). Impact of breastfeeding on the incidence and severity of respiratory syncytial virus (RSV)-associated acute lower respiratory infections in infants: a systematic review highlighting the global relevance of primary prevention. BMJ global health, 8(2), e009693. https://doi.org/10.1136/bmjgh-2022-009693

Mineva, G., & Philip, R. (2023). Impact of breastfeeding on the incidence and severity of respiratory syncytial virus bronchiolitis in infants: systematic review. Rural and remote health, 23(1), 8088. https://doi.org/10.22605/RRH8088

Tonon, K. M., Chutipongtanate, S., Morrow, A. L., & Newburg, D. S. (2024). Human Milk Oligosaccharides and Respiratory Syncytial Virus Infection in Infants. Advances in nutrition (Bethesda, Md.), 15(6), 100218. https://doi.org/10.1016/j.advnut.2024.100218

Plaza-Díaz, J., Fontana, L., & Gil, A. (2018). Human Milk Oligosaccharides and Immune System Development. Nutrients, 10(8), 1038. https://doi.org/10.3390/nu10081038