Pfizer to Seek FDA Emergency Authorization for 3rd Booster Shot to Strengthen Protection Against Delta Variant

Photo credit: Joel Saget, AFP via Getty Images

Pfizer will seek emergency use authorization from the FDA for a third booster shot of its Covid-19 vaccine, specifically intended to increase the immune response to the delta variant of the virus and to combat a drop-off in antibodies approximately six months after inoculation.

The highly contagious delta variant has spread rapidly and currently accounts for most new Covid-19 infections in the U.S.

Pfizer, like Moderna, received FDA emergency use authorization for a two-dose vaccine.

Dr. Mikael Dolsten, Pfizer’s chief scientific officer, told the AP on Thursday that their study of data from Israel suggested that antibody levels jump five- to 10-fold after a third booster shot, compared to the levels after their second dose. There was also a trend, he noted, after six months that the highly contagious delta variant “can cause infections and mild disease.”

“The Pfizer vaccine is highly active against the Delta variant,” Dolsten said in an interview. But after six months, he said, “there likely is the risk of reinfection as antibodies, as predicted, wane.”

Pfizer will officially make the request for EUA in August, Dolsten said.

According to Reuters, Pfizer will conduct a placebo-controlled efficacy trial of this third booster shot with 10,000 participants in the fall. This trial would not be completed in time for the EUA, but would factor into the FDA’s eventual decision to issue final approval or not.

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