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Pfizer and BioNTech Are Testing a Third Booster Shot to Bolster Its Covid-19 Vaccine Against New Variants

The companies plan to offer booster shots to those who participated in their initial clinical trial.

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This story originally appeared on Business Insider

Pfizer and BioNTech on Thursday morning announced plans to study the effects of a third Covid-19 vaccine dose in participants from the drug's original clinical trial.

Dado Ruvic/Reuters via BI
Pfizer says it will continue its COVID-19 vaccine clinical trial with the testing of third-dose booster shots.

The companies plan to offer booster shots to as many as 144 participants six to 12 months after they received their second dose of the vaccine. The Phase 1 trial began last May, so some people who participated would already be eligible for a third dose.

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

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

Preliminary data suggests the Pfizer-BioNTech 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 Pfizer is preparing for the possibility that it might 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, the chairman and CEO of Pfizer, said in a press release.

Pfizer joins Moderna and AstraZeneca in effort to address variants

Moderna also announced this week the development of three different booster shots meant to address the virus variants. The company has already shipped one new version of its 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 a new vaccine that targets the B.1.351 variant.

Related: FDA Says Johnson & Johnson's One-Dose Vaccine Is Safe and Effective

AstraZeneca and Oxford University have also started working on a "next generation" Covid-19 vaccine to address variants. The codevelopers told Reuters 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 with 72% effective in the U.S. 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 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.