Will COVID vaccines need a booster shot to combat variants? Here’s what to know

Katie Camero
·3 min read

There are now three coronavirus variants of concern spreading in the U.S., federal health officials say — one from the U.K., another from Brazil and a third from South Africa.

Scientists are paying extra attention to the last one.

Both authorized COVID-19 vaccines in the U.S. appeared to protect against the new variants in laboratory tests, but further research by Pfizer-BioNTech and Moderna have confirmed that its shots showed significantly weaker responses against the South African variant.

Experts say this suggests immunity gained from either coronavirus vaccine may dwindle earlier against the variant from South Africa compared to other variants.

Both companies recently announced they will begin testing what they call booster shots to amp up immune responses to the variant, which seems to spread more easily between people.

Booster shots are just repeat vaccinations, typically after a first series of shots as a child, experts at Harvard Medical School said. A common one is for the tetanus vaccine, which the Centers for Disease Control and Prevention recommends every 10 years to ensure constant protection from serious disease.

That’s what Pfizer and Moderna hope to accomplish for COVID-19, although it’s unknown if the coronavirus will need updated vaccines each year to tackle new strains, like the flu does.

“In the event that this virus continues to mutate in this direction, and a year from now is still circulating in some way, we think it’s prudent that we have tools like a booster vaccine to address that,” Moderna President Stephen Hoge told The Wall Street Journal.

During laboratory tests, Moderna said there was a “sixfold reduction” in the antibodies’ effectiveness against the South African variant, called B.1.351, while there was no “significant impact” on protection against the U.K. variant.

“Out of an abundance of caution,” Moderna is developing a new booster “with strain-specific spike proteins” against the South African variant that could be administered after two doses of the original shot. The decision was made in an effort to get ahead of the virus if it does change enough to render the vaccine useless.

The company is testing the booster in pre-clinical and Phase 1 studies in the U.S., according to a Monday news release. It’s also studying if a third dose of its COVID-19 vaccine will improve immune response against B.1.35 and future variants.

“We’re doing it today to be ahead of the curve, should we need to,” Dr. Tal Zaks, Moderna’s chief medical officer, told The New York Times. “I think of it as an insurance policy. I don’t know if we need it, and I hope we don’t.”

Pfizer also said its vaccine protects against the variant from South Africa despite some reductions in antibody effectiveness.

“We are already laying the groundwork to respond quickly if a variant of SARS-CoV-2 shows evidence of escaping immunity by our vaccine,” Pfizer told Reuters.

President Joe Biden recently announced travel restrictions on most non-U.S. citizens in South Africa trying to travel into the U.S. to prevent the more transmissible variant from spreading more in the country. They will go into effect Saturday.