First Exposure

Protecting infants against RSV infection: Vaccination during pregnancy or a monoclonal antibody for infants  

Authored by Dr. Tali Bogler and reviewed by First Exposure Medical Review Team. 

Dr. Tali Bogler, MD, CCFP, MScCH, is a Medical Advisor at First Exposure, a Family physician, and Chair of Family Medicine Obstetrics at St. Michael’s Hospital, an Assistant Professor, Department of Family and Community Medicine and Investigator at Li Ka Shing Knowledge Institute. 

This health topic is an expert opinion about protecting infants against RSV infection: vaccination during pregnancy or a monoclonal antibody for infants.  

* The information provided is the expert opinion of the First Exposure Medical Advisors. It is for informational purposes only and does not replace medical care and advice from a healthcare provider. Please contact your healthcare provider if you have any concerns or to discuss any questions that you believe may be relevant to you or your baby. In case of emergency, please go to the emergency room or call 911.  

 If you do not have a healthcare provider please go to: Finding a Healthcare Provider 

Clinical scenario: 

I am currently in my third trimester of pregnancy and expecting to have my baby in the winter. I heard there are new options in Canada to protect my baby against RSV infection, including a vaccine in pregnancy. Where can I learn more about my options to protect my baby against RSV infection? 

 

Q. What is Respiratory Syncytial Virus (RSV)?

A. RSV is a very common and highly contagious RNA virus, infecting almost all children by the age of two years old and adults as well. In Canada, increased RSV activity typically occurs between late fall and early spring. Every year, RSV places a substantial burden on infants and children, their caregivers and families, as well as the health care system.

 

Q. What are the symptoms of RSV?

A. Most people infected with RSV have mild to moderate cold-like symptoms (e.g. cough, runny nose, fever) and will recover within 1-2 weeks with supportive treatments (e.g., rest and fluids). Infants who have RSV may not cough or have a runny nose. Instead, their symptoms may be fussiness/irritability, difficulty breathing, nasal congestion and a decrease in energy and appetite. In more severe cases, lower respiratory tract infections (e.g. pneumonia) develop and may result in hospitalization and/or intensive care unit admission.

 

Q. How is RSV spread?

A. RSV is spread through respiratory droplets which are created when an infected person coughs or sneezes. The virus can also be spread by touching something that has the virus on it (contaminated surfaces) then touching your mouth, nose or eyes without washing or sanitizing your hands

 

Q. Is RSV infection a concern in pregnancy?

A. At this time, RSV infection during pregnancy has not been associated with a higher risk of serious complications. There is one study suggesting higher rates of hospitalization in pregnant women with an RSV infection compared to non-pregnant women. This is insufficient to determine if there is an increased risk of severe RSV infection in pregnancy. Some respiratory infections (e.g. flu) are more severe in pregnancy, particularly in the third trimester. Based on this, it is suggested to take the necessary precautions to reduce exposure to respiratory viruses during pregnancy (see below How to reduce the spread of RSV). There are not enough data to determine if having RSV infection in pregnancy increases the risk for adverse pregnancy outcomes. 

 

Q. Is RSV infection a concern in infants?

A. RSV can cause serious complications in infants, especially those less than 6 months of age. These include severe lower respiratory tract disease and pneumonia, leading to hospitalization and Intensive Care Unit (ICU) admission. Infants with certain medical conditions (e.g., prematurity) are at higher risk of severe RSV disease. Of note, healthy infants born at term make up most of the infants hospitalized or with severe RSV disease.

 

Q. How can I protect my infant from severe RSV infection?

A. There are several products approved by Health Canada to reduce the risk of severe RSV infection. Until recently, palivizumab (Synagis®), was the only product available for reducing the risk of severe infection and it was reserved for high-risk infants. Palivizumab is a monoclonal antibody which requires several monthly injections. Monoclonal antibodies act like the antibodies produced by one’s immune system to help fight infections such as RSV infection.

 In 2023, Health Canada approved two new products. The approval of these new products provides an opportunity to expand protection from severe RSV disease to all infants and not just those at high risk. 

The two products available to protect children against RSV Infection include: 

  • A vaccine, RSVpreF (Abrysvo®), given in pregnancy between 32-36 weeks, to those who are expected to give birth near the start or during the RSV season, to help protect their infants against severe RSV infection for the first 6 months of life.
  • A monoclonal antibody nirsevimab (Beyfortus®), that is given directly to infants/children, in the form of a one-time injection, to help protect against severe RSV infection for 6 months.    

Canada’s National Advisory Committee on Immunization (NACI) recommends use of the monoclonal antibody administered to the infant, over the RSVpreF vaccine given in pregnancy. This recommendation is based on the higher efficacy of the monoclonal antibody in reducing the rates of severe RSV infections and RSV infections that required medical attention. The monoclonal antibody protection also lasted longer and has a good safety profile. The RSVpreF vaccine given in pregnancy might be recommended for those who do not wish to give their child, or do not have access to, the monoclonal antibody.  

Q. If I get the vaccine in pregnancy can my baby also get the monoclonal antibody?

A. Only one option, either the RSVpreF vaccine or the monoclonal antibody, is recommended to protect infants, except in specific cases:

 

Q. Are both products readily available in Canada?

A. Availability and eligibility for these products vary by province and territory. It is important for new or expectant parents to speak with their healthcare provider and/or local public health unit to learn about their options to protect their infant(s) against RSV infection. Choosing between the RSVpreF vaccine given in pregnancy, or the monoclonal antibody depends on one’s personal preference, availability in one’s province or territory, and cost.

As of fall 2024, Ontario, Quebec and Nunavut are offering the new monoclonal antibody product free of cost to all infants in their first RSV season, and high-risk children up to 24 months of age. Ontario is also offering the RSVpreF vaccine, free of cost, during pregnancy. For more information on programs and eligibility, please visit:  

Ontario Respiratory Syncytial Virus (RSV) prevention programs 

Quebec Immunization against respiratory syncytial virus (RSV) infections 

The following questions relate specifically to the RSV vaccine in pregnancy: 

Q. How does the RSV vaccine (RSVpreF (Abrysvo®)) given in pregnancy work to protect infants?

A. The RSVpreF (Abrysvo) vaccine administered at 32-36 weeks of pregnancy triggers the maternal immune system to produce antibodies against RSV. These antibodies pass to the fetus during pregnancy, protecting the infant from birth until 6 months of age. Based on two clinical trials, the vaccine given during pregnancy, was shown to be effective in reducing the risk of severe RSV disease in infants, and the number of RSV infections that required medical attention, particularly during the first few months of life. This same immunization strategy is used to prevent pertussis (whooping cough) in infants when Tetanus, Diphtheria, and Pertussis (Tdap) vaccine is administered during pregnancy.

 

Q. Can I get an RSV infection from the RSV vaccine?

A. You cannot get an RSV infection from the vaccine. The RSVpreF (Abrysvo®)) vaccine contains inactivated (cannot cause infection) pieces of the RSV virus.

 

Q. Does receiving the RSV vaccine in pregnancy increase the chance of a birth defect?

A. Most pregnancies result in a healthy baby, but there are chances of complications and unexpected outcomes. These chances are called baseline risks. In Canada, the baseline risk of major birth defects is 3-5%. This means that 3-5 out of 100 babies born in the general population in Canada will be born with a major birth defect. The first trimester is the most sensitive period for developing birth defects. As the vaccine is administered at 32-36 weeks of pregnancy, we do not expect it to cause birth defects. The available studies did not find that receiving the RSV vaccine in pregnancy increases the risk of birth defects above the baseline risk.

 

Q. Does receiving the RSV vaccine in pregnancy increase the chance of preterm birth?

A. There are inconsistent data on the association between the RSVpreF vaccine and preterm birth. However, no increased risk of preterm birth was reported in high-income countries including Canada. Out of an abundance of caution, Health Canada limited the RSVpreF vaccine to be administered between 32-36 weeks’ gestation, after the chance of severe prematurity has passed. 

 

Q. How to reduce the spread of RSV and other respiratory illness?

A. In addition to the products discussed above, additional ways to protect your infant and family include:

  • frequent handwashing  
  • avoiding touching one’s face  
  • sneezing or coughing into one’s elbow or tissue (instead of into hands) 
  • cleaning and sanitizing surfaces that are frequently touched  
  • avoiding others who are sick 
  • staying home when sick 
  • wearing a mask (adults) 

 

KEY MESSAGES: 

It is important for new or expectant parents to speak with their healthcare provider and/or local public health unit to learn about their options to protect their infant(s) against RSV infection this upcoming RSV season.  

Prenatal care providers should provide counseling in the third trimester about the options to protect the infant(s) against RSV infection, so the expectant parents are properly informed prior to birth. 

 Additional resources: 

PCMCH Resources on RSV for Parents, Expectant Parents and Healthcare Providers  

Ministry of Ontario Abrysvo® (RSV Vaccine) in pregnancy fact sheet  

Immunize Canada RSV Vaccine in Pregnancy 

Vaccines in Pregnancy Canada RSV 

Key References

Abrams EM, Doyon-Plourde P, Davis P, Brousseau N, Irwin A, Siu W, Killikelly A. Burden of disease of respiratory syncytial virus in infants, young children and pregnant women and people. Can Commun Dis Rep. 2024 Jan 1;50(1-2):1-15. [PMID: 38511049]. [PMC10949905. 

Ares-Gómez S, Mallah N, Santiago-Pérez MI, Pardo-Seco J, Pérez-Martínez O, Otero-Barrós MT, et al. Effectiveness and impact of universal prophylaxis with nirsevimab in infants against hospitalisation for respiratory syncytial virus in Galicia, Spain: initial results of a population-based longitudinal study. Lancet Infect Dis. 2024 Aug;24(8):817-828. Epub 2024 Apr 30. Erratum in: Lancet Infect Dis. 2024 Jul;24(7):e419. [PMID: 38701823]. 

Kampmann B, Madhi SA, Munjal I, Simões EAF, Pahud BA, Llapur C, et al. Bivalent 

prefusion F vaccine in pregnancy to prevent RSV illness in infants. N Engl J Med. 2023 Apr 20;388(16):1451-1464. Epub 2023 Apr 5. [PMID: 37018474]. 

Ontario Ministry of Health. Respiratory Syncytial Virus [Internet]. Government of Ontario [updated 2024 September 03; cited 2024 September 15]. Available from: https://www.ontario.ca/page/respiratory-syncytial-virus 

Public Health Agency of Canada. Summary of the National Advisory Committee on Immunization (NACI) Statement of May 17, 2024 Statement on the prevention of respiratory syncytial virus (RSV) disease in infants. Ottawa, ON: His Majesty the King in Right of Canada; 2024 [updated May 17, 2024; cited 2024 September 15]. Available from: https://www.canada.ca/content/dam/phac-aspc/documents/services/publications/vaccines-immunization/national-advisory-committee-immunization-summary-statement-prevention-respiratory-syncytial-virus-disease-infants/naci-summary-2024-05-17.pdf. 

Public Health Agency of Canada. An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI) Statement on the prevention of respiratory syncytial virus (RSV) disease in infants. Ottawa, ON: His Majesty the King in Right of Canada; 2024 [updated May 17, 2024; cited 2024 September 15]. Available from: https://www.canada.ca/content/dam/phac-aspc/documents/services/publications/vaccines-immunization/national-advisory-committee-immunization-statement-prevention-respiratory-syncytial-virus-disease-infants/naci-statement-2024-05-17.pdf. 

Simões EAF, Center KJ, Tita ATN, Swanson KA, Radley D, Houghton J, et al. Prefusion F 

protein–based respiratory syncytial virus immunization in pregnancy. N Engl J Med. 2022 Apr 28;386(17):1615-26. [PMID: 35476650]. 

Son M, Riley LE, Staniczenko AP, Cron J, Yen S, Thomas C, Sholle E, Osborne LM, Lipkind HS. Nonadjuvanted Bivalent Respiratory Syncytial Virus Vaccination and Perinatal Outcomes. JAMA Netw Open. 2024 Jul 1;7(7):e2419268.[PMID: 38976271; PMCID: PMC11231799]. 

U.S. Food and Drug Administration. Respiratory Syncytial Virus Vaccine (Proposed Trade Name: Abrysvo) Pfizer [briefing document from Vaccines and Related Biological Products Advisory Committee Meeting May 18, 2023]. Washington DC: Food and Drug Administration; 2023 [cited 2024 September 15]. Available from: https://www.fda.gov/media/168185/download 

Vaccines in Pregnancy Canada. Respiratory Syncytial Virus (RSV) Vaccine Calgary: Vaccines in Pregnancy Canada; 2024 [updated April 10, 2024; cited 2024 September 15]. Available from: https://www.vaccinesinpregnancycanada.ca/vaccines/rsv. 

Disclaimer

First Exposure does not offer health care treatment. If you have an urgent question about your pregnancy or your baby’s health, you should contact your health care provider directly. If you don’t have a health care provider and you live in Ontario, you have a variety of health care options. In the case of an emergency, visit a hospital emergency room or call 911.