Why do some people think that RSV vaccines increase the risk of preterm birth for pregnant women?

An unadjuvanted GSK maternal RSV vaccine was stopped because there were more preterm births in the vaccine vs placebo group, but only for part of the study, from April to December 2021.

The usual suspects...

Do RSV Vaccines Increase the Risk of Preterm Birth?

Now remember, RSV infections are common and RSV is the leading cause of hospitalizations for infants in the United States. They are also a common reason for visits to the doctor and ER and tragically, each year, RSV is associated with at least 100-300 deaths in young children.

So that's why many of us were excited when the first RSV vaccine, Abrysvo, was approved for pregnant women at 32 to 36 weeks gestation.

"In the clinical trials, more preterm births were observed among RSVpreF (Abrysvo) vaccine recipients than among placebo recipients, although the differences were not statistically significant. It is unclear whether preterm birth was caused by the vaccine or simply due to chance. Available data are insufficient to establish or exclude a causal relationship between preterm birth and RSVpreF (Abrysvo). To reduce the potential risk of preterm birth when administering maternal RSV vaccine, FDA approved the vaccine for use from 32 through 36 weeks of pregnancy."

Frequently Asked Questions About RSVpreF (Abrysvo) Vaccine for Pregnant People

While it is not known yet if Abrysvo is actually associated with preterm births, by giving the dose at 32 to 36 weeks, you can avoid the risk of extreme prematurity while getting the benefits of this vaccine! And further post-marketing safety studies will be done to assess the risk of pre-term births.

To get protection against RSV, either pregnant mothers should get Abrysvo during weeks 32 through 36 6/7 weeks of pregnancy (September through January) or newborns/infants should get Beyfortus during RSV season (October through March).

Why not just wait even longer, until you are about to deliver before getting the dose?

It takes a few weeks to build up an immune response and transfer the RSV antibodies to the baby across the placenta before they are born. These antibodies then provide about six months of protection to the baby against medically-attended RSV associated lower respiratory tract infection and hospitalization.

Why get the RSV vaccine while you are pregnant instead of Beyfortus for your baby later?

You can get either, as one isn't preferred over the other. One thing to keep in mind though, Beyfortus has been in short supply this season, which could leave your baby unprotected. Getting Abrysvo while you are pregnant can help ensure that your baby gets protected.

Do RSV Vaccines Increase the Risk of Preterm Birth?

Do RSV Vaccines Increase the Risk of Preterm Birth?

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