Pfizer to study booster shot aimed at virus variant

Pfizer and its partner BioNTech said Thursday they are beginning a study to test whether a third shot of their COVID-19 vaccine will help protect against variants of the virus.

In addition, the companies said they are in “ongoing discussions” with regulators about the potential need to study an updated version of the vaccine to fight a variant first identified in South Africa that has raised concerns about reducing the effectiveness of vaccines.

Pfizer said there is not yet evidence that its vaccine will be less effective against the variants, but it is preparing in case further evidence emerges.

The company is beginning a study that will give a third shot to people who participated in the company’s phase 1 clinical trial of the vaccine. The third shot would come six to 12 months after the initial two shots.

Simply giving a third shot of the existing vaccine would avoid the need to develop and manufacture an updated vaccine.

“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,” said Pfizer CEO Albert Bourla.

“At the same time, we are making the right investments and engaging in the appropriate conversations with regulators to help position us to potentially develop and seek authorization for an updated mRNA vaccine or booster if needed,” he added.

Lab studies have shown the Pfizer and Moderna vaccines produce lower levels of antibodies against the South African variant, but it is unclear how much that will translate to a drop in effectiveness. Both companies have said they think their vaccines will still be protective, but they are also preparing backup plans.

Moderna said Wednesday that it has sent doses of an updated vaccine against the South African variant to the National Institutes of Health for study.