Pfizer is set to seek US permission for a third dose of its Covid-19 vaccine, saying on Thursday that another injection within 12 months could significantly boost immunity and possibly help ward off the latest disturbing mutant of the coronavirus.
Research in several countries shows that the Pfizer vaccine 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 infections in the United States. United.
Two doses of most vaccines are essential for building high levels of anti-virus antibodies against all versions of the coronavirus, not just the delta variant – and most countries around the world are still desperate to get those initial protective doses. as the pandemic continues to rage.
But antibodies naturally decline over time, so studies are also underway to tell if and when boosters might be needed.
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Pfizer’s Dr Mikael Dolsten told The Associated Press on Thursday that early data from the company’s booster study suggests that people’s antibody levels increase five to ten times after a third dose, compared to at their second dose months earlier.
In August, Pfizer plans to seek emergency clearance from the Food and Drug Administration for a third dose, he said.
Why might this be important to combat the delta variant?
Dolsten pointed to data from Britain and Israel showing that the Pfizer vaccine “neutralizes the delta variant very well.” The hypothesis, he said, is that when the antibodies drop low enough, the delta virus could eventually cause a mild infection before the immune system returns.
But FDA clearance would only be a first step – it wouldn’t automatically mean Americans would be offered recalls, warned Dr William Schaffner, a vaccine expert at Vanderbilt University Medical Center. Public health authorities should decide if they are 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 as we are currently trying to get people to get the first dose.”
Currently, only about 48% of the U.S. population is fully vaccinated – and parts of the country have much lower vaccination rates, places where the delta variant is booming. On Thursday, Dr Rochelle Walensky, director of the Centers for Disease Control and Prevention, said this led to “two truths” – heavily immune swathes of America are returning to normal as hospitalizations increase in other places.
“This rapid increase is disturbing,” she said: A few weeks ago, the delta variant accounted for just over a quarter of new cases in the United States, but now it represents just over 50% – and in some places, like parts of the Midwest, up to 80 percent.
Also on Thursday, researchers at the Institut Pasteur in France reported new evidence that a full vaccination is essential.
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In lab tests, the blood of dozens of people who received their first dose of Pfizer or AstraZeneca vaccines “barely inhibited” the delta variant, the team reported in the journal Nature. But weeks after receiving their second dose, almost all had what the researchers considered to be an immune boost strong enough to neutralize the delta variant – even if it was a little less potent than against earlier versions of the virus.
French researchers also tested unvaccinated people who had survived a coronavirus attack and found their antibodies were four times less potent against the new mutant. But a single dose of the vaccine dramatically increased their antibody levels – triggering cross-protection against the delta variant and two other mutants, the study found. This supports public health recommendations that Covid-19 survivors get vaccinated rather than relying on natural immunity.
Laboratory experiments add to real-world data that mutations in the delta variant do not escape the most widely used vaccines in Western countries, but underscore that it is crucial to get more of the world vaccinated before the virus is no longer evolving.
British researchers have found that two doses of the Pfizer vaccine, for example, protect 96% against hospitalization with the delta variant and are 88% effective against symptomatic infections. The finding was echoed last weekend by Canadian researchers, while a report from Israel suggested that protection against mild delta infection may have declined, to 64%.
Whether fully vaccinated people should still wear masks in places where the delta variant is increasing is a growing question. In the United States, the CDC maintains that people who are fully vaccinated do not need to. Even before the arrival of the delta variant, vaccines weren’t perfect, but the best evidence suggests that if vaccinated people nonetheless contract the coronavirus, they will have much milder cases.
“Let me stress that if you’ve been vaccinated you get a very high level of protection,” Dr Anthony Fauci, the US government’s top infectious disease expert, said Thursday.
In the United States, case rates have been rising for weeks and the hospitalization rate has started to rise, rising 7% from the previous seven-day average, Walensky told reporters Thursday. However, deaths remain on the decline on average, which some experts say is at least in part due to high vaccination rates among people 65 and older – who are among the most likely to contract serious illness.
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