This sheet is about exposure to the respiratory syncytial virus (RSV) vaccine in pregnancy and while breastfeeding. This information is based on available published literature. 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.
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 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 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 people who are 32-36 weeks pregnant who have never received the 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 person 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). CDC has information about the maternal RSV vaccine and nirsevimab here: https://www.cdc.gov/rsv/immunizations-protect-infants/index.html.
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 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 published data to try to understand if an exposure, like the RSV vaccine, might increase the chance of birth defects in a pregnancy. Studies on people 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 people 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 people 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.
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 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 male 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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OTIS/MotherToBaby encourages inclusive and person-centered language. While our name still contains a reference to mothers, we are updating our resources with more inclusive terms. Use of the term mother or maternal refers to a person who is pregnant. Use of the term father or paternal refers to a person who contributes sperm.
