Pfizer is seeking US approval for a third dose of its COVID-19 vaccine and said Thursday that a new shot within 12 months could dramatically boost immunity and perhaps help ward off the latest worrying coronavirus mutant.
Research from several countries shows that the Pfizer shot and other widely used COVID-19 vaccines offer strong protection against the highly contagious delta variant, which spread rapidly around the world and now accounts for most new American infections.
Two doses of most vaccines are critical for developing high levels of antiviral antibodies against all versions of the coronavirus, not just the delta variant ̵
But antibodies naturally decrease over time, so studies are also underway to tell if and when boosters may be needed.
On Thursday, Pfizer’s dr. Mikael Dolsten to the Associated Press that early data from the company’s booster study suggest that people’s antibody levels jump five to ten times after a third dose compared to their second dose months earlier.
In August, Pfizer plans to ask the Food and Drug Administration for urgent approval of a third dose, he said.
Why might it matter to fight the delta variant? Dolsten pointed to data from the UK 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 can eventually cause a mild infection before the immune system kicks back.
But FDA approval would only be a first step – it would not automatically mean that Americans were offered boosters, warned Dr. William Schaffner, a vaccine expert at Vanderbilt University Medical Center. Public health authorities have to decide if they are really necessary, 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 a new dose would be “a huge effort while we are currently striving to get people to the first dose.”
Currently, only about 48% of the US population is fully vaccinated – and some parts of the country have much lower immunization rates, in places where the delta variant is increasing. On Thursday, Dr. Rochelle Walensky, director of the Centers for Disease Control and Prevention, said it led to “two truths” – heavily immunized shards in America return to normal while admissions rise elsewhere.
“This rapid increase is alarming,” 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% – and in some places, such as parts of the Midwest , as much as 80%.
Also on Thursday, researchers from the French Pasteur Institute reported new evidence that full vaccination is critical.
In laboratory studies, blood from several dozen people hardly inhibited their first dose of the Pfizer or AstraZeneca vaccines, the team reported in the journal Nature. But weeks after receiving their second dose, almost everyone had what the researchers considered an immune system strong enough to neutralize the delta variant – even though it was slightly less potent than against previous versions of the virus.
The French researchers also tested unvaccinated people who had survived a coronavirus attack and found their antibodies four times less potent against the new mutant. But a single dose of vaccine dramatically increased their antibody levels – sparks cross-protection against the delta variant and two other mutants, the study found. It supports public health recommendations that COVID-19 survivors be vaccinated instead of relying on natural immunity.
The laboratory experiments add real-world data that the mutations of the delta variant do not escape the vaccines most commonly used in Western countries, but emphasize that it is crucial to get more of the world immunized before the virus develops even more.
Researchers in the UK found two doses of the Pfizer vaccine, for example, are 96% protective against hospitalization with the delta variant and 88% effective against symptomatic infection. This finding was repeated last weekend by Canadian researchers, while a report from Israel suggested that protection against mild delta infection may have dipped lower to 64%.
Whether the fully vaccinated still need to wear masks in places where the delta variant fluctuates is a growing question. In the United States, the CDC maintains that fully vaccinated people do not need it. Even before the delta variant came, the vaccines were not perfect, but the best evidence suggests that if vaccinated people get coronavirus anyway, they will have much milder cases.
“Let me emphasize that if you were vaccinated, you have a very high level of protection,” said Dr. Anthony Fauci, the US government’s leading expert on infectious diseases, on Thursday.
In the United States, cases have risen for several weeks and the number of hospital admissions has begun to cross, rising 7% from the previous seven-day average, Walensky told reporters on Thursday. However, deaths are on average down, which some experts believe is due, at least in part, to high vaccination rates in people 65 and older – who are among the most susceptible to serious illness.
Associated Press author Mike Stobbe contributed to this story.
The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. AP is solely responsible for all content.
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