Drugmaker Pfizer said July 28 that data suggest a third dose of its COVID-19 vaccine provides a strong boost in protection against the highly contagious delta coronavirus variant.
The company said in an earnings report that initial findings suggest antibody levels against the delta variant were five times higher among people ages 18 to 55 and 11 times higher among those ages 65 to 85 after the third dose of its vaccine compared to after the second dose.
It also said there’s a potential for an up to “100-fold increase in delta neutralization” after a third dose.
Pfizer said it will be publishing more “definitive data” on the third dose and that “all accumulated data will be shared as part of the ongoing discussions” with regulatory agencies in the coming weeks.
Pfizer and BioNTech, the companies that developed one of the three COVID-19 vaccines available in the U.S., said July 8 they were developing an updated version of their vaccine to target the delta variant.
The companies said they planned to start clinical trials in August if given regulatory approval.
They said a third dose of their current vaccine “has the potential to preserve the highest levels of protective efficacy against all currently known variants including delta,” but that they’re developing the updated version to remain “vigilant.”
But the Centers for Disease Control and Prevention and the U.S. Food and Drug Administration said shortly after that fully vaccinated Americans do not need a booster COVID-19 shot “at this time.”
“We continue to review any new data as it becomes available and will keep the public informed,” the agencies said. “We are prepared for booster doses if and when the science demonstrates that they are needed.”
Dr. Anthony Fauci, the nation’s top infectious disease expert, said July 11 on CNN’s State of the Union that booster vaccines “theoretically” could help protect vulnerable people but that the recommendations from the CDC and FDA are based on data and information currently available on the need for boosters.
“There are studies being done now, ongoing as we speak, about looking at the feasibility about if and when we should be boosting people,” he said. “So this isn’t something we say ‘no we don’t need a boost right now, the story’s ended forever.’ No, there’s a lot of work going on to examine this in real time to see if we might need a boost.”
It’s unclear exactly how long the COVID-19 vaccines offer protection against the virus.
Pfizer CEO Albert Bourla said in May that its likely there will be a need for a third shot within eight to 12 months after initial vaccination but that data are still preliminary.
On July 28, he said on the podcast “In the Bubble with Andy Slavitt” that Pfizer’s vaccine works very well against the delta variant but that the “duration of this protection is challenged after six months.”
“So the vaccine is very well protecting — the second dose — until the first six months and then we start to see waning efficacy,” Bourla said.
Moderna has also said its likely its vaccine will require a booster shot, and CEO Stéphane Bancel previously said the company will make a third vaccine available to Americans by the fall, McClatchy News reported.
Fauci said April 11 that health officials will know more about the need for booster shots by this fall and that the need for another dose of the vaccine depends on “correlate immunity” against the coronavirus.
“When the slope starts coming down you can predict when you’re going to get below the safe level or you could start seeing breakthrough infections,” Fauci said on ABC’s “This Week.” “I believe by the time we get to the end of the summer and the beginning of the fall, we’ll have a pretty good idea of whether we definitely or not need to give people boosts and when we need to give it to them.”
Pfizer’s July 28 report comes during increased concerns about the delta variant, which has been spreading across the U.S and sparking COVID-19 outbreaks.
On July 27, the CDC updated its face mask guidance, saying fully vaccinated people should again wear mask in public indoor setting if they live in areas with substantial or high COVID-19 transmission.
CDC director Rochelle Walensky said during a news briefing that new data shows that the delta variant behaves differently than other strains of the coronavirus and that in “rare occasions” some vaccinated people infected with it may be able to spread the virus to others.