| 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.
Researchers in Britain found two doses of the Pfizer vaccine, for example, are 96 percent protective against hospitalization with the delta variant and 88 percent effective against symptomatic infection. That finding was echoed last weekend by Canadian researchers, while a report from Israel suggested protection against mild delta infection may have dipped lower, to 64 percent.
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.
“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.”
Hours after Pfizer’s announcement, U.S. health officials issued a statement saying fully vaccinated Americans don’t need a booster yet.
U.S. health agencies “are engaged in a science-based, rigorous process to consider whether or when a booster might be necessary,” the FDA and Centers for Disease Control and Prevention said in a joint statement. That work will include data from the drug companies, “but does not rely on those data exclusively,” and any decision on booster shots would happen only when “the science demonstrates that they are needed,” the agencies said.
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, the CDC director, said that’s leading to “two truths” — highly immunized swaths of America are getting back to normal while hospitalizations are rising in other places.
“This rapid rise is troubling,” she said: A few weeks ago the delta variant accounted for just over a quarter of new U.S. cases, but it now accounts for just over 50 percent – and in some places, such as parts of the Midwest, as much as 80 percent.
In the U.S., case rates have been rising for weeks and the rate of hospitalizations has started to tick up, rising 7 percent from the previous seven-day average, Walensky told reporters Thursday. However, deaths remain down on average, which some experts believe is at least partly due to high vaccination rates in people 65 and older – who are among the most susceptible to severe disease.
