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  • Writer's pictureEscalate Life Sciences

Pfizer gets first positive result for an RSV vaccine in pregnant women

The shot kept newborns from getting severe respiratory infections, paving the way for the drugmaker to seek approval before its top rivals.

Pfizer’s experimental vaccine for respiratory syncytial virus kept newborns from getting severe respiratory infections for the first six months of life after their mothers received the shot during pregnancy, the company said Tuesday.

Success in the Phase 3 trial, which independent data monitors stopped early because of clear signs of efficacy, was the first for a maternal RSV vaccine. The findings enable Pfizer to become the first company with a marketed vaccine that can prevent infections in both newborns and older people, the two populations most affected by RSV.

While GSK, Johnson & Johnson and Moderna are trailing Pfizer on a shot for pregnant women, the company could face some immediate competition from an antibody drug called Beyfortus and developed by AstraZeneca and Sanofi. A committee advising Europe’s drug regulator has recommended Beyfortus as a preventive treatment. The Food and Drug Administration has given the drug a breakthrough therapy designation as well, speeding up its review.

Pfizer’s trial, called MATISSE, enrolled 7,400 pregnant women and randomized half to receive the vaccine and the other half to receive a placebo. The study met one of its two main goals, reducing severe medically attended lower respiratory tract infections. The babies of mothers who received the vaccine had 69% fewer cases six months after birth, Pfizer said.

The vaccine wasn’t able to reach statistical significance in preventing non-severe infections requiring medical attention, however. According to Pfizer, there were 51% fewer cases at six months of age in babies whose mother received the vaccine. Though comparing drugs across trials can be difficult, Beyfortus succeeded in that measure in clinical testing, reducing medically attended lower respiratory tract infections by 75% compared to a placebo.

Pfizer said it will submit the maternal vaccine data to the FDA by the end of 2022, joining the results it generated in adults age 60 and older.

“There is the potential that, subject to regulatory approval, by late 2023 or early 2024 we could have the only RSV maternal vaccine on the market, along with an RSV vaccine for older adults that has high efficacy and is well-tolerated with no safety concerns,” CEO Albert Bourla said during a conference call with analysts today. “Combined, the two indications represent a potential multibillion-dollar peak revenue opportunity.”

While GSK got a jump on Pfizer by generating the first data for an RSV vaccine in older adults, it has suspended clinical trial work in pregnant women because of a safety signal.

About 6.5 million babies 6 months and younger are infected with RSV each year around the world, and 45,000 die.

Published Nov. 1, 2022

Jonathan GardnerSenior Reporter

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