Can you guess the leading cause of infant hospitalizations in the United States? You might think accidents, allergic reactions, or the flu, but the answer is actually respiratory syncytial virus (RSV). Every year, RSV sends 58,000 to 80,000 children under the age of 5 to the hospital.
Having a baby in the fall or winter has always meant that parents need to be extra careful about RSV. Fortunately, in 2023 two new ways to protect infants against this virus became available: a vaccine given to women between 32 and 36 weeks of pregnancy and an antibody (passive immunization) that is given directly to babies after birth. Today, we’re covering some of the most common questions we get at MotherToBaby about RSV prevention.
Q: What is the maternal RSV vaccine? When is it given?
The maternal RSV vaccine (brand name Abrysvo®) is a protein subunit vaccine (it contains proteins the body needs to make antibodies against RSV). The vaccine does not contain live virus that can cause RSV. When a woman gets the RSV vaccine during pregnancy, the antibodies she makes can also pass to the developing fetus. These antibodies can help protect the baby from RSV during the first 6 months of life.
The Abrysvo® RSV vaccine can be given to women who are 32 to 36 weeks pregnant who have not received a maternal RSV vaccine in a previous pregnancy. The RSV vaccine is only recommended for use during pregnancy between September and January in most of the United States.
Q. What is an infant RSV antibody? When is it given?
Infant antibodies, also called passive immunizations, are another effective way to help protect babies from RSV. Two RSV antibodies are currently available: nirsevimab (Beyfortus®) and clesrovimab (Enflonsia®). The RSV antibody is recommended for infants younger than 8 months who are entering their first RSV season if their mothers did not receive the maternal RSV vaccine during pregnancy. Infants and children ages 8 to 19 months who are at high risk for severe RSV illness and entering their second RSV season may also be eligible for the antibody. The RSV antibody is available between October and March for most of the United States and starts working immediately after it is given.
For more information about timing, eligibility, and benefits of infant RSV antibodies, talk with your child’s pediatrician.
Q: Is one of these options better than the other?
Patients can choose either the maternal vaccine or the infant antibody. Both are great options for protecting infants against RSV, and there is currently no preference for one over the other. A slight benefit of getting the RSV vaccine during pregnancy is that most babies will be born with immediate protection if the vaccine is given at least 2 weeks before delivery. Some parents might also prefer the maternal vaccine because it avoids an extra injection (shot) for the baby.
Q. How do we know the RSV vaccine is ok to get in pregnancy?
Studies on the Abrysvo® RSV vaccine have not found a higher chance of birth defects. It’s also reassuring to note that the vaccine is given in the third trimester (between 32 and 36 weeks), which is past the critical period when most birth defects could happen.
Early clinical trials on the vaccine observed slightly more preterm births in women who received the Abrysvo® RSV vaccine than in those who did not (5.7% in the vaccinated group vs. 4.7% in the placebo group). However, newer data from larger studies has not found a higher chance of preterm birth following RSV vaccination in pregnancy. Check out the MotherToBaby RSV vaccine fact sheet for more information on this topic.
Q. If I got an RSV vaccine in my last pregnancy, do I need to get it again in my next pregnancy?
The simple answer is no. At this time, the maternal RSV vaccine is only recommended for women who have not gotten it in a previous pregnancy. Researchers need time to determine if getting the vaccine once can provide ongoing protection for future pregnancies, or if a booster dose is needed in every pregnancy.
If you received the RSV vaccine during a previous pregnancy and are pregnant again, your baby can get an infant RSV antibody to help ensure they are protected.
Making Your Choice
No matter whether you decide on the maternal RSV vaccine or an infant RSV antibody, you’re making a great choice to protect your baby from RSV! Still have questions? Remember that MotherToBaby can be reached by chat, text, phone, or email with questions about the RSV vaccine or any other exposure in pregnancy or while breastfeeding.
