Early-stage study shows third dose of vaccine offers a higher level of protection, companies say
Pfizer Inc. and partner BioNTech SE have submitted data to U.S. health regulators needed to cleara Covid-19 booster shot among the general public.
The companies said Monday they sent to the U.S. Food and Drug Administration results from a small, early-stage study showing a third dose of their vaccine generated higher levels of neutralizing antibodies against the original virus and against the Beta and Delta variants than the standard two-dose regimen.
The addition of the third dose also appeared safe in the trial, the companies said.
Given the immune response boost from a third dose, the companies said, a booster shot within six months to a year after the second shot might help maintain protection against symptomatic Covid-19.
Pfizer and BioNTech are also conducting a larger late-stage study evaluating whether a third dose safely provides more protection. The companies said they expect those results shortly and will then submit the data to the FDA.
The FDA is considering a broader booster strategy, which the agency could issue in the next few weeks.
Two doses of the Pfizer-BioNTech shot, given three weeks apart, are authorized for people ages 12 years and older.
Some physicians and scientists in the U.S. say there isn’t a clear answer yet on whether boosters are needed for the general population, partly because of evidence that shows vaccines continue to be highly effective at preventing severe disease.
Studies indicate the vaccine is still highly effective in people six months after their second dose. Yet there is some evidence its efficacy might diminish over longer periods, and the shot isn’t as effective againstt he Delta variant, prompting research into adding a third dose.
Last week, the FDA authorized a third dose of an mRNA vaccine like the Pfizer-BioNTech shot for certain people with weakened immune systems, in a bid to bolster their immune defenses against Covid-19.
In the early-stage study looking at a booster among generally healthy people, subjects got a third 30-microgram dose, Pfizer and BioNTech said. The subjects received the extra dose eight to nine months after receiving their second dose.
Then researchers measured in subjects their levels of neutralizing antibodies, which play a crucial role in protection against the virus, the companies said.
The levels rose against the initial strain of the virus, as well as the Beta and Delta variants, the companies said. After the booster dose, neutralizing antibodies against the variants were similar to the earlier strain, the companies said.
Pfizer presented some of the scientific data during its second-quarter earnings presentation last month, but hasn’t detailed the results yet. After a third shot, antibody levels were up more than five times among people ages 18 to 55 and more than 11 times in people ages 65 to 85, compared with two doses, according to Pfizer’s data.