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 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 RSV can cause an infection in the lungs, such as pneumonia. 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 who are born preterm (before 37 weeks), and people with weakened immune systems have a higher chance of developing a severe RSV infection.
To learn more about RSV, see the MotherToBaby 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 the vaccine is given at the recommended time during pregnancy (32-36 weeks), these antibodies can pass to the fetus. It takes about 2 weeks after getting the vaccine during pregnancy for antibodies to fully pass to the fetus. The antibodies 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®. Abrysvo® is a protein subunit vaccine. It does not contain a live virus that can cause RSV. Major medical groups including the Centers for Disease Control and Prevention (CDC) recommend the Abrysvo® RSV vaccine for women who are 32-36 weeks pregnant and have not received the RSV vaccine in a previous pregnancy. The vaccine is recommended for use during pregnancy from September to January in most of the United States.
Women who received an RSV vaccine during any previous pregnancy are not recommended to get an RSV vaccine again in a current pregnancy. Instead, they should talk to their healthcare providers about protecting their babies against RSV with antibodies given directly to the baby after delivery. CDC has information about the maternal RSV vaccine and infant antibodies here: https://www.cdc.gov/rsv/vaccines/protect-infants.html.
Other RSV vaccines (such as Arexvy® and mResvia®) are not approved for use in pregnancy. If you believe you received one of these vaccines while pregnant, talk with your healthcare provider about the recommendations for protecting your baby from RSV. Experts do not recommend any special monitoring if a woman was given an incorrect RSV vaccine in pregnancy.
Can getting the RSV vaccine make it harder for me to get pregnant?
The Abrysvo® RSV vaccine is recommended for women who are already pregnant (32-36 weeks) and for older adults. 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 recommended for women who are already pregnant (32-36 weeks) and for older adults. If a woman happens to get an RSV vaccine before pregnancy, there is no recommended waiting period before getting 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 Abrysvo® RSV vaccine can increase the chance of miscarriage. The 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 Abrysvo® RSV vaccine, might increase the chance of birth defects in a pregnancy.
Studies on the Abrysvo® RSV vaccine during pregnancy have not found a higher chance of birth defects. The vaccine is recommended for use during the third trimester of pregnancy, which is past the time when birth defects are most likely to happen.
Does getting the RSV vaccine in pregnancy increase the chance of other pregnancy-related problems?
Studies have not found an increased chance of most pregnancy-related problems, such as low birth weight (weighing less than 5 pounds, 8 ounces [2500 grams] at birth).
In early studies on the Abrysvo® RSV vaccine given between 24 and 36 weeks of pregnancy, there were slightly more preterm births (birth before 37 weeks) among women who got the vaccine compared to women who did not. However, ongoing studies on the vaccine have not found a higher chance of preterm birth. The recommendation to get the vaccine closer to the end of pregnancy (between 32 and 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.
Some studies have seen a slightly higher chance of problems related to high blood pressure among women who receive the Abrysvo® RSV vaccine in pregnancy compared to women who do not. It is not clear if these problems are related to the vaccine or to other factors. Other studies have not found a higher chance of problems related to high blood pressure.
Does getting the RSV vaccine in pregnancy affect future behavior or learning for the child?
Studies have not been done to see if the RSV vaccine can increase the chance of behavior or learning issues for the child.
Breastfeeding and the RSV vaccine:
Studies have not been done on the RSV vaccine in women who are breastfeeding. CDC states that protein subunit vaccines like Abrysvo® pose no risk for women who are breastfeeding or their infants (see https://www.cdc.gov/vaccines/hcp/imz-best-practices/special-situations.html#cdc_report_pub_study_section_5-breastfeeding-and-vaccination). Be sure to talk to your healthcare provider about all your breastfeeding questions.
If a man gets the RSV vaccine, could it affect his 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 make healthy sperm) 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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