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Respiratory Syncytial Virus (RSV) Vaccine (Abrysvo®)

Last Update: 02 Apr 2025

Welcome to our fact sheet on respiratory syncytial virus (RSV) vaccine (Abrysvo®) during pregnancy and breastfeeding/ chestfeeding. This information is based on available published literature. It should not take the place of medical care and advice from your healthcare provider.

The HEALTHY PREGNANCY HUB team is collaborating with MotherToBaby to share information on this topic. The original version is available here (August 2024).

Serene, our chatbot, can also answer your questions about medications during pregnancy.

Please note that this fact sheet is based on United States information and has been adapted for Canada, with a review by our Canadian experts. Minor differences may exist between the two countries. Always consult your healthcare professional for information tailored to your situation.

1. What is it?

What is respiratory syncytial virus?

Respiratory syncytial virus (RSV) is a virus that can cause an infection of the respiratory (breathing) tract. RSV spreads easily from person to person through droplets when an infected person coughs or sneezes. It can also spread through direct contact with surfaces that have the virus on them. Most cases of RSV are mild and cause only cold-like symptoms. However, sometimes having RSV can lead to an infection in the lungs, such as pneumonia (also called lower respiratory tract disease). Serious symptoms like fever, severe cough, wheezing, rapid breathing, and cyanosis (blue skin caused by not having enough oxygen in the body) might require hospitalization or the use of a ventilator to help the person breathe. Infants, babies that are born preterm (before 37 weeks), and people with weakened immune systems have a higher chance of developing severe RSV infection. 

What is the RSV vaccine?

The RSV vaccine causes a person to make antibodies against RSV. When a person gets the RSV vaccine at the recommended time during pregnancy (32-36 weeks), the antibodies she makes can pass to the developing baby. It takes about 2 weeks after getting the vaccine in pregnancy for antibodies to fully pass to the developing baby. These antibodies can help protect the baby from severe RSV infection for about 6 months after they are born. 

The only RSV vaccine approved for use in pregnancy in the United States (US) is called Abrysvo® (other available RSV vaccines are approved for use in older adults but not for use in pregnancy). Abrysvo® is a protein subunit vaccine. It does not contain live virus that can cause RSV. The Centers for Disease Control and Prevention (CDC) recommend the Abrysvo® RSV vaccine for individuals who are 32-36 weeks pregnant who have not received an RSV vaccine in a previous pregnancy. The RSV vaccine is only recommended for use during RSV season. In most regions of the continental US, RSV season is from September to January. However, the timing and severity of RSV seasons can be different from year to year. 

If a pregnant individual has already received an RSV vaccine during any previous pregnancy, she does not need to get an RSV vaccine again in her current pregnancy. Instead, she should talk to her healthcare provider about protecting her baby against RSV with nirsevimab (infant antibody). CDC has information about the maternal RSV vaccine and nirsevimab here: https://www.cdc.gov/rsv/vaccines/protect-infants.html. 

2. What are the risks according to research?

Does getting the RSV vaccine make it harder to get pregnant?

Studies have not been done to see if getting the RSV vaccine can make it harder to get pregnant. 

I just got the RSV vaccine. How long do I need to wait before I get pregnant?

The Abrysvo® RSV vaccine is only recommended for individuals who are already pregnant (32-36 weeks) and for older adults. In the rare event that someone gets the RSV vaccine and is planning a pregnancy, there is no recommendation to wait to get pregnant. 

Does getting the RSV vaccine increase the chance of miscarriage?

Miscarriage is common and can occur in any pregnancy for many different reasons. Studies have not been done to see if the RSV vaccine increases the chance for miscarriage. The RSV vaccine is recommended for use during the third trimester of pregnancy, which is past the time when a miscarriage can happen. 

Does getting the RSV vaccine increase the chance of birth defects? 

Birth defects can happen in any pregnancy for different reasons. Out of all babies born each year, about 3 out of 100 (3%) will have a birth defect. We look at research studies to try to understand if an exposure, like the RSV vaccine, might increase the chance of birth defects in a pregnancy. Studies on individuals who received the Abrysvo® RSV vaccine during pregnancy have not found a higher chance of birth defects. 

Does getting the RSV vaccine in pregnancy increase the chance of other pregnancy-related problems?

A clinical trial looking at over 3,600 individuals who received the Abrysvo® RSV vaccine between 24 and 36 weeks of pregnancy found no increased chance of pregnancy-related problems, such as low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). However, slightly more preterm deliveries were seen in those who received the vaccine. In most cases, the preterm deliveries happened a month or more after getting the vaccine. A newer study looking at over 2,900 pregnant individuals who received the Abrysvo® RSV vaccine did not find an increased chance of preterm delivery. The recommendation to get the vaccine closer to the end of pregnancy (at 32-36 weeks) allows time for antibodies to pass to the baby before delivery but lowers the chance (if there is one) of delivering early from the vaccine, since the vaccine is given closer to full term. 

Does getting the RSV vaccine in pregnancy affect future behavior or learning for the child?

Studies have not been done to see if getting the RSV vaccine can cause behavior or learning issues for the child. 

3. Breastfeeding/ chestfeeding and the RSV vaccine

The Abrysvo® RSV vaccine is only recommended for individuals who are pregnant (32-36 weeks) and for older adults. Studies have not been done on the RSV vaccine in individuals who are breastfeeding/ chestfeeding. The Advisory Committee on Immunization Practices (ACIP) and CDC state that subunit vaccines, like Abrysvo®, pose no risk for individuals who are breastfeeding/ chestfeeding or their infants (see https://www.cdc.gov/breastfeeding/breastfeeding-special-circumstances/vaccinations-medications-drugs/vaccinations.html). Be sure to talk to your healthcare provider about all your breastfeeding/ chestfeeding questions. 

4. Fathers and sperm donors

If a male gets the RSV vaccine, could it affect fertility or increase the chance of birth defects?

Studies have not been done to see if the RSV vaccine could affect a male’s fertility (ability to get a a partner pregnant) or increase the chance of birth defects. In general, exposures that fathers and sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures here.  

Key points

  • The RSV vaccine (Abrysvo®) is a protein subunit vaccine designed to protect babies from respiratory syncytial virus (RSV).
  • The vaccine is recommended for pregnant individuals between 32 and 36 weeks of pregnancy during RSV season.
  • Studies have not found an increased risk of birth defects following vaccination during pregnancy.
  • Current recommendations prioritize vaccination between 32 and 36 weeks to help reduce any potential risk of preterm birth.
  • The vaccine is not expected to pose a risk to individuals who are breastfeeding/ chestfeeding.
  • Talk to your healthcare provider to discuss your options for protecting your baby against RSV.

References

Please click here for references. 

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Disclaimer

HEALTHY PREGNANCY HUB provides a source of information validated by health professionals; however, this information is provided for informational purposes only and should not replace professional advice. Medical standards and practices evolve as new data becomes available, so it is imperative to consult your doctor or a qualified health professional for any questions or concerns regarding your health without delay or omission. It is the responsibility of your treating physician or any other health professional, based on their independent experience and knowledge of the patient, to determine the best way to evaluate and treat you.

HEALTHY PREGNANCY HUB does not specifically recommend or endorse any test, practitioner, treatment, product, or opinion mentioned on our platform. HEALTHY PREGNANCY HUB also does not replace the individual patient assessment based on the examination by the healthcare provider of each patient and the consideration of laboratory data and other patient-specific factors.

The use of the information available on our site is at your own risk. No person involved in the creation, production, promotion, or marketing of HEALTHY PREGNANCY HUB guarantees or represents, expressly or implicitly, anything regarding the information available on the platform, which is provided “as it is”. All warranties are expressly excluded and disclaimed, including but not limited to implied warranties of merchantability or fitness for a particular purpose, as well as any warranties arising by law or otherwise in law or from trade or usage. Any statements or representations made by any other person or entity are void.

While consulting symptoms or other medical information on our platform may guide your discussions with your healthcare professional, this information should not be used to make a medical diagnosis or determine treatment. Before making changes to your supplement or medication regimen, please discuss with your medical team or contact 811 (Canada) to ensure the relevance of these changes to your individual situation.

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MotherToBaby
Organization of Teratology Information Specialists (OTIS)
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Émy Roberge
Centre hospitalier universitaire Sainte-Justine
Anne-Sophie Otis
Centre Hospitalier Sainte-Justine

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