The U.S. Food and Drug Administration (FDA) has been busy in recent weeks. After approving the first over-the-counter contraceptive and the first postpartum depression drug, the agency is taking action in the fight against respiratory syncytial virus (RSV).
The FDA has officially approved a vaccine, Abrysvo, for pregnant women during weeks 32 through 36 of pregnancy that would help protect their babies from RSV.
“RSV is a common cause of illness in children, and infants are among those at highest risk for severe disease, which can lead to hospitalization,” said Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research. “This approval provides an option for health care providers and pregnant individuals to protect infants from this potentially life-threatening disease.”
Safety of the vaccine
Abrysvo was approved for protection against RSV in adults over 60 back in May. To test the efficacy in infants, researchers conducted two clinical trials, the first of which included 3,600 pregnant women who received the Abrysvo vaccines and 3,600 who received a placebo. The second trial cut down the participants to 100 women in each group.
There were a few side effects that emerged in both clinical trials. Many of them were common for any vaccine: muscle pain, headache, pain at the injection site, and nausea.
However, some of the side effects posed health risks to the women and their pregnancies. The studies found that preterm births occurred in 5.7% of the women who received the Abrysvo vaccine, compared with 4.7% of women who received the placebo, though it still is unknown if this is in direct correlation to the drug.
There was also a higher risk of jaundice, low birth weight, and preeclampsia in women who received the vaccine – 1.8% of these women developed the high blood pressure condition, compared with 1.4% who received the placebo.
Researchers found that administering the vaccine in the latest weeks of pregnancy – weeks 32-36 – is likely to lower the risk of preterm birth.
Vaccine efficacy
Based on these two studies, the researchers found that Abrysvo was effective at lowering infants’ risk of developing severe RSV within three months and six months of birth.
One group of study participants included 3,000 pregnant women between 32 and 36 weeks, half of whom received the Abrysvo vaccine, while the other half received a placebo.
Compared to those who didn’t receive the vaccine, the risk of severe lower respiratory tract disease (LRTD) – an infection caused by RSV – decreased by 90% in the first three months of life, and by 76.5% in the first six months of life.
Similarly, the risk of respiratory tract disease was nearly 35% lower in the first three months for those who had been vaccinated, while the risk was over 57% lower in the first six months.
More work will continue to be done on the drug to better understand some of the health risks, including preeclampsia.
