This sheet is about exposure to the respiratory syncytial virus (RSV) vaccine Abrysvo® in pregnancy and while breastfeeding. This information is based on published research studies. It should not take the place of medical care and advice from your healthcare provider.
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.
To learn more about RSV, see MotherToBaby’s fact sheet on RSV Infection here: https://mothertobaby.org/fact-sheets/respiratory-syncytial-virus-rsv/.
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 they make can pass to the developing fetus. 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 women 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 in pregnancy from September to January in most of the United States.
If someone has already received an RSV vaccine during any previous pregnancy, they do not need to get an RSV vaccine again in their current pregnancy. Instead, they should talk to their healthcare provider about protecting their baby against RSV with nirsevimab (infant antibody). The CDC has information about the maternal RSV vaccine and nirsevimab here: https://www.cdc.gov/rsv/immunizations-protect-infants/index.html.
Other RSV vaccines exist, but they are not approved for use in pregnancy. Some brand names for these include Arexvy® and mResvia®. If you believe that you received one of these vaccines while pregnant, contact your healthcare provider to discuss the best way to protect your baby from RSV. Experts do not recommend any special monitoring if people have received the incorrect RSV vaccine.
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 people 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 are no recommendations about waiting periods 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 can increase the chance of 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 Abrysvo® RSV vaccination 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?
Studies have not found an increased chance of pregnancy-related problems, such as low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth). In some studies, RSV vaccination during pregnancy was associated with an increased chance of preterm delivery (birth before 37 weeks). Other studies have not found 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 affect future behavior or learning for the child.
Breastfeeding and the RSV vaccine:
The Abrysvo® RSV vaccine is only recommended for people who are pregnant (32-36 weeks) and for older adults. Studies have not been done on the RSV vaccine in people who are breastfeeding. The Advisory Committee on Immunization Practices (ACIP) and CDC state that subunit vaccines, like Abrysvo®, pose no risk for people who are breastfeeding 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 questions.
If a man 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 men’s fertility (ability to get a partner pregnant) or increase the chance of birth defects. In general, exposures that fathers or sperm donors have are unlikely to increase risks to a pregnancy. For more information, please see the MotherToBaby fact sheet Paternal Exposures at https://mothertobaby.org/fact-sheets/paternal-exposures-pregnancy/.
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