What Expecting Parents Should Know

The Food and Drug Administration (FDA) approved the Abrysvo vaccine for pregnant people in August 202, after researchers found it was safe and effective for preventing lower respiratory tract infections in newborns.

“We now have an RSV vaccine that can prevent serious RSV infection in infants when received during pregnancy,” Dr. Jennifer Thompson, FACOG, an associate professor in the Division of Maternal-Fetal Medicine at Vanderbilt University Medical Center told Healthline.

“By receiving the RSV vaccine during pregnancy, maternal antibodies cross the placenta and provide protection to the newborn. These antibodies help prevent the development of severe RSV lower respiratory tract infection in infants up to 6 months of age,” Thompson said.

The vaccine is made from an inactivated protein from the surface of RSV, known as the fusion glycoprotein, or protein F.

When the vaccine is given to a pregnant person, their immune system responds by producing antibodies against protein F. This allows their immune system to recognize and attack RSV if it encounters the virus later on.

It takes about 2 weeks for the pregnant person’s immune system to produce antibodies following vaccination.

The pregnant person passes the antibodies onto the developing fetus across the placenta, which provides protection against RSV that continues for at least 6 months after birth.

It’s still possible for infants to contract RSV after their birthing parent has received the Abrysvo vaccine in pregnancy. However, the vaccine significantly reduces the newborn infant’s risk of developing RSV infection in general and severe RSV infection mainly.

Researchers found that when pregnant people received the Abrysvo vaccine during weeks 32–36 of pregnancy, it reduced their baby’s risk of lower respiratory tract disease from RSV by 34.7% within 90 days following birth and 57.3% within 180 days after birth.

The vaccine provided even greater protection against severe lower respiratory tract disease, lowering the risk by 91.1% within 90 days after birth and 76.5% within 180 days after birth.

“RSV can be such a devastating disease for some families,” said Thompson, “and to now have a vaccine to offer patients that is safe and effective at preventing severe RSV in infants is wonderful.”

The risk of serious side effects from the Abrysvo vaccine is low. Most side effects are mild and short-lastingg.

“The main side effects that have been reported are similar to other vaccines and include pain at the injection site, headaches, and muscle pain,” said Thompson.

Researchers found the rate of preeclampsia was slightly higher among pregnant people who received the vaccine: 1.8% of those who received the vaccine in a clinical trial developed preeclampsia, compared with 1.4% of pregnant people who received the placebo. The overall rate of preeclampsia remained low.

Researchers also found the rate of preterm birth was slightly higher among pregnant people who received the vaccine (5.7%, compared with those who received a placebo (4.7%). However, they could not determine whether this difference was caused by the vaccine or something else.

The FDA has taken steps to manage the potential risk of preterm birth by approving the Abrysvo vaccine for only those pregnant people who are 32–36 weeks pregnant.

People who have a history of severe allergic reactions to any component of the vaccine shouldn’t receive it. Severe allergic reactions to vaccines are rare.

Pregnant people can speak with their obstetrician to learn more about the potential benefits and risks of getting the RSV vaccine or other immunizations during pregnancy.

Abrysvo is specifically recommended for people who are 32–36 weeks pregnant during RSV season, which lasts from September through January across much of the United States but may vary in some regions. Speak with your doctor if you live in Alaska, Florida, or outside the continental United States to learn about the timing of RSV season in your region.

If you recently gave birth and didn’t receive the Abrysvo vaccine at least 2 weeks before delivery, talk with your doctor to learn whether your baby should receive immunization against RSV with the monoclonal antibody nirsevimab (Beyfortus).

Beyfortus can lower the risk of serious RSV infection among infants, but it’s available in the United States only in limited supplies. It may be given to an infant as a single injection shortly before or during their first RSV season — and in some cases, shortly before their second RSV season.

Most babies who are born to a birthing parent who received the Abrysvo vaccine at least 2 weeks before delivery don’t require immunization with Beyfortus later on.

But some babies with high risk factors for severe infection may benefit from immunization from Beyfortus, even if their birthing parent did receive the Abrysvo vaccine.

This includes certain infants who:

• were born prematurely and have chronic lung disease
• have cystic fibrosis with severe disease
• have severe immunocompromise
• are American Indian or Alaska Native

A physician may also recommend immunization with the monoclonal antibody palivizumab (Synagis) in rare cases. This immunization is only given to children under the age of 24 months who have certain health conditions that raise their risk of severe RSV disease.

Limiting contact with people who are sick, washing hands regularly with soap and water or alcohol-based hand cleanser, and wearing face masks in public may also help prevent RSV or other respiratory infections.

Talk with your doctor to learn more about strategies to prevent and manage RSV infections.

To help protect young infants from RSV illness, the CDC encourages people who are 32–36 weeks pregnant during RSV season to get a single dose of Pfizer’s bivalent RSVpreF vaccine (Abrysvo). This is sometimes known as the maternal RSV vaccine.