Respiratory Syncytial Virus
(RSV) Vaccine
Respiratory syncytial virus, or RSV, usually causes mild cold-like symptoms, but it can lead to severe illness in some people. Children under age 5, and particularly babies 6 months and younger, are most vulnerable to severe illness if they get RSV. Each year, thousands of young children are hospitalized because of RSV illness.
There are two ways to protect babies against RSV:
Pregnant people can get the RSV vaccine Abrysvo during weeks 32 through 36 of pregnancy during RSV season (which starts September 1 and lasts through January 31 in most areas of the United States), OR
Babies born from September 1 through March 31 can be immunized with a monoclonal antibody, nirsevimab (Beyfortus), from birth until they are 8 months of age. Babies born from April to August can be immunized with nirsevimab in October.
Most infants do not need both.
Source: https://www.cdc.gov/rsv/vaccines/protect-infants.html
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Abrysvo is an RSV vaccine that is approved for pregnant people and older adults. It is given as a single dose during weeks 32 through 36 of pregnancy during RSV season.
There is another RSV vaccine called Arexvy. This vaccine is not approved for pregnant people.
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The vaccine works with your body’s immune system to make antibodies against the virus. When the vaccine is given during pregnancy, the antibodies made in your body cross the placenta and enter the fetal bloodstream. This process takes about 2 weeks. By the time your baby is born, they will already have antibodies that give some protection against RSV.
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Studies show that the vaccine:
Reduces the risk of serious RSV complications in babies by 70% within 6 months after birth.
Reduces the risk of a baby being hospitalized due to RSV by 67% within 6 months after birth.
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The most commonly reported side effects are pain at the injection site, headache, muscle pain, and nausea.
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Nirsevimab (also called Beyfortus) is a shot given to babies to protect against RSV. It delivers anti-RSV antibodies directly into the baby’s bloodstream. It is given to babies younger than 8 months who are born during RSV season or entering their first RSV season. Newborns can get nirsevimab even before they leave the hospital. One dose of nirsevimab has been shown to prevent severe illness due to RSV in babies up to 5 months old by 80%.
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Minor side effects include redness and swelling at the injection site and a mild rash. No serious side effects have been reported.
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If you were pregnant last year and received Abrysvo, and you are pregnant again this year, it’s recommended that you don’t get another dose. Instead, your baby should receive nirsevimab.
If you haven’t received Abrysvo before, you can choose between getting Abrysvo at 32 through 36 weeks of pregnancy during RSV season OR immunizing your baby with nirsevimab from birth up to age 8 months.
The vaccine given during pregnancy and the infant immunization are safe and effective ways to prevent illness caused by RSV in infants. Your healthcare professional can help you decide which option is best for you and your baby. Here is a comparison of the two options:
| ABRYSVO (RSV vaccine given during pregnancy) | NIRSEVIMAB (Beyfortus) (RSV immunization given to babies) | |
|---|---|---|
| Who is it for? | Pregnant people who have not received Abrysvo in a previous pregnancy Given during weeks 32 through 36 of pregnancy during the RSV season (September 1st through January 31st) | • Infants up to age 8 months entering their first RSV season, AND • Infants and children aged 8 – 19 months entering their second RSV season |
| How effective is it at preventing severe RSV in babies? | Reduces severe complications of RSV in babies by 70% within 6 months of birth | Reduces the risk of a baby being hospitalized due to RSV by 80% within 5 months of birth |
| What are the side effects? | Injection site pain, headache, muscle pain, nausea, and fever | Rash and injection site pain |
| What are the benefits? | • Your baby is born protected against RSV because the antibodies are already present. • Abrysvo may give better protection against RSV variants than nirsevimab. • It reduces the number of injections your baby gets. • There may be ongoing protection through breastfeeding. | • The antibodies in the immunization are delivered directly into the baby’s bloodstream (instead of being passed across the placenta),which may result in stronger protection. • The protection from the immunization may be more long-lasting than with Abrysvo. |
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Quick Facts
RSV can cause serious illness in infants, especially those under six months. Vaccination during pregnancy helps protect babies right from birth.
The RSV vaccine Abrysvo is recommended for pregnant people during weeks 32 through 36 of pregnancy during RSV season, which typically lasts from September 1st through January 31st.
Abrysvo works with your immune system to create RSV antibodies that pass across the placenta, providing your baby with protection against RSV after birth.
Abrysvo reduces the risk of severe RSV complications by 70% and hospitalization by 67% within six months of birth.
If you don’t get the RSV vaccine during pregnancy, infants can receive the monoclonal antibody nirsevimab, which is highly effective in preventing severe RSV.
Glossary
Antibodies: Proteins made by the immune system in response to a foreign substance, such as a virus.
Immune system: The cells and organs that protect the body against foreign substances, such as bacteria and viruses.
Placenta: A special organ that develops during pregnancy. It allows the transfer of nutrients, antibodies, and oxygen to the fetus. It also makes hormones that sustain the pregnancy.
This resource was supported by the Society for Maternal-Fetal Medicine (SMFM) and the Centers for Disease Control and Prevention (CDC) cooperative agreement CDC-RFA-DD-23-0004 Enhancing Partnerships to Address Birth Defects, Infant Disorders and Related Conditions, and the Health of Pregnant and Postpartum People. The views expressed by the authors do not necessarily reflect the official policies of the Department of Health and Human Services nor represent an endorsement by the U.S. Government.
The videos on this page are sponsored by a grant from Pfizer, Inc. No content should be considered a solicitation, promotion, or advertisement for any Pfizer product.
Last Updated: October 2024