Can you guess the leading cause of infant hospitalization in the United States? You might think of accidents, allergic reactions, or the flu, but the answer is actually respiratory syncytial virus (RSV). Each 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 always meant parents had to be extra careful about RSV. Fortunately, two new ways to protect babies from this virus became available in 2023: a vaccine given to women between 32 and 36 weeks pregnant, and an antibody (passive vaccination) 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 RSV maternal vaccine? When is it given?
The RSV parent vaccine (trade name Abrysvo®) is a protein subunit vaccine (it contains proteins that 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.
Abrysvo® RSV vaccine can be given to women who are 32 to 36 weeks pregnant who have not received 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®). RSV antibody is recommended for infants younger than 8 months who are entering their first RSV period if their mothers did not receive the maternal RSV vaccine during pregnancy. Infants and children 8 to 19 months of age who are at high risk for severe RSV disease and are 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 as soon as it is given.
For more information about the timing, suitability, and benefits of RSV antibodies for infants, talk to 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 excellent options for protecting infants from 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 may also prefer the maternal vaccine because it avoids an additional injection (vaccine) for the baby.
Q. How do we know the RSV vaccine is OK to get pregnant?
Studies on Abrysvo® The RSV vaccine has not been found to increase the chance of birth defects. It is 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 occur.
Early clinical trials for the vaccine saw slightly more premature births in women who received Abrysvo® RSV vaccine compared to those who did not (5.7% in the vaccinated group vs. 4.7% in the placebo group). However, newer data from larger studies have not found a greater chance of preterm birth after RSV vaccination in pregnancy. See the MotherToBaby RSV vaccine fact sheet for more information on this topic.
Q. If I had 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 had it in a previous pregnancy. Researchers need time to determine whether getting the vaccine once can provide continued protection for future pregnancies, or whether a booster dose is needed in each pregnancy.
If you received the RSV vaccine during a previous pregnancy and are pregnant again, your baby may receive an infant RSV antibody to ensure it is protected.
Making your choice
Whether you decide on the maternal RSV vaccine or an infant RSV antibody, you are 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.
