3-shot combo? Pfizer, BioNTech roll COVID-19 booster trial as real-world data back first vaccine

As Pfizer and BioNTech start testing whether a third dose of their COVID-19 shot can help fend off new coronavirus variants, a massive real-world study has confirmed that its first, two-dose regimen is 94% effective.

The third-dose study now underway will gauge the effects of that follow-up dose on circulating and new COVID-19 virus variants.

At the same time, the companies are in talks with the FDA and EMA about studying a new booster specifically designed to tackle new variants. They're hoping to validate "future modified mRNA vaccines with a regulatory pathway similar to what is currently in place for flu vaccines,” according to a press release.

BioNTech CEO Ugur Sahin said the partners are "evaluating a second booster in the current regimen as well as preparing for a potential rapid adaption of the vaccine to address new variants which might escape the current version of our mRNA-based vaccine."

The Pfizer announcement follows news that mRNA vaccine rival Moderna has sent a newly designed booster shot for NIH testing. The booster targets the South African variant of the virus. Moderna is also looking at potential multivariant boosters and at its original shot as a half-dose booster.

Still, Pfizer thinks a third dose of its current shot will amp protection against variants. CEO Albert Bourla told NBC News the company believes the third dose “will raise the antibody response 10- to 20- fold.”

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The trial will study two groups, ages 18-55 and 65-85, from its Phase 1 trial begun last May. Participants will receive a third dose of the vaccine, now called Comirnaty, exactly the same as the first two they received six to 12 months ago.

The FDA earlier this week signaled its willingness to work with vaccine makers to speed up booster development. The agency is working on expedited review rules for the follow-up shots.

There’s no need “to start at square one with any of these products—we recognize we are in a pandemic and we need to arm healthcare providers with the most appropriate tools to fight this pandemic on the front lines,” acting FDA Commissioner Janet Woodcock, M.D., said in an early February statement.

While the variant studies ramp up, a real-world study out of Israel confirms Comirnaty’s effectiveness.

Researchers found 46% effective at preventing infection 14 to 20 days after the first dose, and 92% effectiveness seven days after the second dose. The vaccine proved even better at preventing symptomatic infection at 57% and 94% for the same time periods.

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The study, published Wednesday in The New England Journal of Medicine, was led by scientists at the Clalit Research Institute in Tel Aviv and included experts from Harvard University and Boston Children’s Hospital. The study tracked 596,618 people vaccinated with Comirnaty matched to the same number of unvaccinated controls.

While the study dates from Dec. 20 through Feb. 1, likely pre-dating widespread capture of emerging coronavirus varients, the researchers confirmed the vaccine's role in stemming the pandemic. It specifically concluded that Comirnaty is highly effective against serious illness, hospitalizations and death.

“These results strengthen the expectation that newly approved vaccines can help to mitigate the profound global effects of the Covid-19 pandemic,” the report finds.