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.

You may have heard that the Centers for Disease Control and Prevention (CDC) recently recommended a new vaccine for use in the third trimester of pregnancy. Known as Abrysvo^TM, the vaccine helps protect newborns against severe cases of respiratory syncytial virus (RSV). RSV is the leading cause of infant hospitalization in the United States, with anywhere from 58,000-80,000 hospitalizations occurring each year among children younger than 5. Even more upsetting is that 100-300 children under age 5 die from RSV every year. With these statistics in mind, this new RSV vaccine is exciting news for infants and their families.

Ava, 24 weeks along with her first pregnancy, contacted the MotherToBaby live chat service early one morning with some questions about the new RSV vaccine. First, she wanted to understand how vaccinating a pregnant woman could provide protection for a baby. As a Teratogen Information Specialist, I was happy to answer this question for Ava. I started by explaining that when a person gets vaccinated, their body makes antibodies. These antibodies protect the body against the actual infection if a person is exposed to the virus or bacteria later in life. During pregnancy, the antibodies that a pregnant woman makes after being vaccinated can cross the placenta and pass to the developing baby, providing the newborn with some protection against the infection during the first few months of life.

I went on to explain that although the RSV vaccine is new, the idea of getting a vaccine during pregnancy to protect the baby (called “passive immunity”) has been around for some time. The Tdap vaccine, which protects against tetanus, diphtheria, and pertussis (whooping cough), has been recommended for use in pregnancy since 2011. Whooping cough is another infection that can be very serious for newborns, so having protection from birth as a result of maternal vaccination is ideal. The flu shot and COVID-19 vaccine can also pass antibodies to the developing baby during pregnancy. This is great news since newborns can’t get their own flu or COVID-19 shots until 6 months of age and need to rely on passive immunity in the meantime.

Next, Ava had a question about when she should get the RSV vaccine. She had plans to get her flu shot and Tdap vaccine at her next prenatal visit at 28 weeks. She wanted to know if she could get the RSV vaccine at the same time. Although these three vaccines (along with the updated COVID-19 vaccine) can all be given on the same day, the RSV vaccine should be given during a specific timeframe in order to pass as many antibodies as possible to the baby. Experts recommend that the RSV shot be given between 32 and 36 weeks of pregnancy. This allows enough time for RSV antibodies to pass to the baby before delivery.

With this recommendation in mind, Ava decided that her prenatal appointment at 32 weeks would be the perfect time to get the RSV vaccine. She had seen firsthand just how serious RSV can be when her 1-month-old niece was hospitalized with RSV last winter, so she didn’t want to take any chances with forgetting to get the RSV vaccine during her pregnancy.

Before we ended the chat, I mentioned to Ava that there is also a shot called nirsevimab (Beyfortus^TM) that can be given directly to babies under 8 months of age. Also known as a monoclonal antibody, this shot is another way to protect infants against severe RSV disease. Most babies do not need nirsevimab if their mom received the RSV vaccine during pregnancy. I suggested Ava talk with her healthcare provider about the pros and cons of both options.

Although having to remember to get another vaccine in pregnancy can feel like just one more thing a pregnant woman needs to add to their never-ending to do list, the decision to vaccinate can prevent serious complications from RSV, and possibly even save the baby’s life. Here at MotherToBaby we are happy to go over the current recommendations for vaccines in pregnancy and answer any questions that you may have. Don’t hesitate to call, chat, text, or email with any questions about the RSV vaccine or other exposures during pregnancy. You can also check out our newest fact sheet about this vaccine here https://mothertobaby.org/fact-sheets/respiratory-syncytial-virus-rsv-vaccine-abrysvo/.  

References:

Centers for Disease Control and Prevention. 2023. RSV Vaccination for Pregnant Women. Available at: https://www.cdc.gov/vaccines/vpd/rsv/public/pregnancy.html

Centers for Disease Control and Prevention. 2023. RSV Surveillance & Research. Available at: https://www.cdc.gov/rsv/research/index.html