vials of the Pfizer-BioNTech Covid-19 vaccine are prepared to be administered to front-line health care workers under an emergency use authorization at a drive up vaccination site from Renown Health in Reno, Nevada on December 17, 2020.

  • Pfizer and BioNTech will study whether a third dose of their Covid-19 vaccine is safe and effective.
  • The companies will offer booster shots to those who participated in their initial clinical trial.
  • Booster shots may be necessary to keep up with the coronavirus' mutations and new variants.
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Pfizer and BioNTech announced this morning that they plan to study the effects of a third Covid-19 vaccine dose in participants from its original clinical trial.

The companies will offer booster shots to up to 144 participants six to 12 months after they received their second dose of the vaccine. The Phase 1 trial kicked off in May 2020, so some people who participated are already eligible for their third doses.

Although the formulation of the booster shot is identical to that of the first two doses, testing out the safety and efficacy of a third shot now could pave the way for the development of variant-specific shots later on.

The B.1.351 variant, which was first identified in South Africa, has been found to have several mutations on the spike protein. This could pose problems for existing vaccines and antibodies that target that part of the virus.

Preliminary data suggests that the Pfizer vaccine could protect against B.1.351 as well as B.1.1.7, a more transmissible variant that first appeared in the UK. But the company is preparing for the possibility that they may eventually need to create additional vaccines that target the variants.

"While we have not seen any evidence that the circulating variants result in a loss of protection provided by our vaccine, we are taking multiple steps to act decisively and be ready in case a strain becomes resistant to the protection afforded by the vaccine," Albert Bourla, chairman and CEO of Pfizer, said in a press release.

Pfizer joins Moderna and AstraZeneca in the effort to address the variants

Moderna also announced this week the development of three different booster shots that could work against the virus variants. The company has already shipped one new version of their vaccine to the National Institutes of Health for testing, and the clinical trial will begin "very soon," Moderna CEO Stéphane Bancel told Insider's Allison DeAngelis

Two other Moderna booster shots are also in progress, along with an entirely new vaccine targeted at the B.1.351 variant.

AstraZeneca and Oxford University have also started working on a "next generation" Covid-19 vaccine to address the new variants. The co-developers told Reuters that the new shot could be available this fall.

As for the ongoing trial of Johnson & Johnson's single-dose vaccine candidate, it was found to work relatively well against the B.1.351 variant. The latest data says the shot was 64% effective in South Africa, compared to 72% effective in the US and 61% effective in Latin America. That vaccine is yet to be authorized by the Food and Drug Administration, but it could be rolled out as early as next week.

Even if the Covid-19 vaccines protect against variants, we may need boosters anyway

People may need booster shots to stay protected against Covid-19 after their initial immunity wanes, Insider's Aylin Woodward wrote in November.

"With human coronaviruses, you can get repeatedly infected - you're not immune for life, you're immune for some time," Florian Krammer, a vaccinologist at the Icahn School of Medicine at Mount Sinai, told Woodward. "There's no reason to think this coronavirus will behave differently."

If existing Covid-19 vaccines fail down the road, experts may consider recommending a booster shot - similar to the seasonal flu vaccine, or an MMR booster.

While we don't yet know if that'll be necessary, efforts like Pfizer's and Moderna's booster trials are meant to evaluate the safety and efficacy of a third dose ahead of time, all while closely monitoring emerging variants.

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