Pfizer looks ahead

Studies researching if and when booster would be necessary

Company researching if and when a third vaccine booster would be necessary.

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 virusfighting antibodies against all versions of the coronavirus, not just the delta variant.

Antibodies naturally wane over time, so studies also are under way 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.

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, considering the number of people yet to be vaccinated.

“The vaccines were designed to keep us out of the hospital” and continue to do so despite the more contagious delta variant, he said. Giving another dose would be “a huge effort while we are at the moment striving to get people the first dose.”

Currently only about 48 percent of the U.S. population is fully vaccinated — and some parts of the country have far lower immunization rates, places where the delta variant is surging. On Thursday, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said that’s leading to “two truths” — highly immunized swaths of America are getting back to normal while hospitalizations are rising in other places.

Also Thursday, researchers from France’s Pasteur Institute reported new evidence that full vaccination is critical. In laboratory tests, blood from several dozen people given their first dose of the Pfizer or Astrazeneca vaccines “barely inhibited” the delta variant, the team reported in the journal Nature. But weeks after getting their second dose, nearly all had what researchers deemed an immune boost strong enough to neutralize the delta variant.

The French researchers also tested unvaccinated people who had survived a bout of the coronavirus, and found their antibodies were four-fold less potent against the new mutant. But a single vaccine dose dramatically boosted their antibody levels. That supports public health recommendations that COVID-19 survivors get vaccinated rather than relying on natural immunity.