Pfizer to study safety, immune response of third dose of COVID-19 vaccine

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Posted at 4:54 PM, Feb 25, 2021
and last updated 2021-02-25 17:00:48-05

TAMPA, Fla. — Pfizer is taking a new step in the fight against COVID-19. The company announced Thursday it will study the safety and immune response of a third dose of its COVID-19 vaccine.

“What I think they’re hoping to do is to try to see if they can improve that immune response, the antibody response, by having a booster dose,” said USF Health associate professor Dr. Michael Teng.

The study is part of the company’s strategy to find out the effectiveness of a third dose against evolving variants. Pfizer will offer Phase 1 participants a chance to get a booster of the current vaccine six to 12 months after getting their initial two doses.

ABC Action News asked Dr. Teng what a third dose would do. He explained we already have a series of vaccines with three doses or more, like for Hepatitis B or polio.

“Every time you get another dose, that boosts your immune system,” said Teng. “I think what they’re hoping with the third dose is that they can tweak that immune response to have it better recognize these potential variants of concern.”

The CDC notes we don’t know how long protection lasts for people who are vaccinated and experts are trying to learn more about both natural and vaccine-induced immunity. Dr. Teng says his question is would a third dose be necessary? Right now, he says we don’t have that answer.

“My suspicion is that this test will tell us whether this is a feasible flu shot like-thing, so that if we do need an annual shot for SARS-CoV-2, that we do have the ability to make it in a very quick way as well," said Teng.

Pfizer says participants will be looked at when they get the third dose, then one week and one month after. Those participants will continue to be followed in the study for up to two years as originally planned.

“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. This booster study is critical to understanding the safety of a third dose and immunity against circulating strains,” said Albert Bourla, Pfizer's Chairman and Chief Executive Officer.