Pfizer to seek FDA authorization for 3rd Covid vaccine dose

Pfizer is about to seek U.S. authorization for a third dose of its Covid-19 vaccine, saying Thursday that another shot within 12 months could dramatically boost immunity and maybe help ward off the latest worrisome coronavirus mutant.

Research from multiple countries shows the Pfizer shot and other widely used Covid-19 vaccines offer strong protection against the highly contagious delta variant, which is spreading rapidly around the world and now accounts for most new U.S. infections.

Two doses of most vaccines are critical to develop high levels of virus-fighting antibodies against all versions of the coronavirus, not just the delta variant — and most of the world still is desperate to get those initial protective doses as the pandemic continues to rage.

But antibodies naturally wane over time, so studies also are underway to tell if and when boosters might be needed.

On Thursday, Pfizer’s Dr. Mikael Dolsten told The Associated Press that early data from the company’s booster study suggests people’s antibody levels jump five- to 10-fold after a third dose, compared to their second dose months earlier.

In August, Pfizer plans to ask the Food and Drug Administration for emergency authorization of a third dose, he said.

Why might that matter for fighting the delta variant?

Dolsten pointed to data from Britain and Israel showing the Pfizer vaccine “neutralizes the delta variant very well.” The assumption, he said, is that when antibodies drop low enough, the delta virus eventually could cause a mild infection before the immune system kicks back in.

But FDA authorization would be just a first step — it wouldn’t automatically mean Americans get offered boosters, cautioned Dr. William Schaffner, a vaccine expert at Vanderbilt University Medical Center. Public health authorities would have to decide if they’re really needed, especially since millions of people have no protection.

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