mRNA vaccines vs. variants: 3 promising updates

Pfizer has been studying the effectiveness of its COVID-19 vaccine in countries hit hard by virus variants, and Moderna has been testing booster shots' ability to fight variants in individuals who have been previously vaccinated.

Below are three key updates about Pfizer and Moderna's efforts to tackle variants:

1. Pfizer's COVID-19 vaccine was effective at preventing COVID-19 infection caused by B.1.1.7, the coronavirus variant first identified in the U.K., and B.1.351, the variant first identified in South Africa, according to a study published May 5 in the New England Journal of Medicine.
   
   Researchers looked at data from more than 200,000 people that was pulled from Qatar’s COVID-19 databases between Feb. 1 and March 31. About half of Qatar's COVID-19 infections during that period were caused by B.1.351, and 44.5 percent were caused by B.1.1.7, according to data sequencing conducted between Feb. 23 and March 18.
   
   The study found that Pfizer's vaccine was 87 to 89.5 percent effective at preventing infection caused by  B.1.1.7 among people who had received their second dose at least two weeks prior.
   
   Pfizer's vaccine was 72.1 to 75 percent effective at preventing infection caused by B.1.351 among people who had received their second dose at least two weeks prior.
   
   B.1.351 is "the nastiest of all the variants of concern," according to Laith Abu-Raddad, PhD, one of the study's authors and an infectious disease epidemiologist at Weill Cornell Medicine-Qatar. "It’s not the 95 percent we were hoping, but the 75 percent is really great," he said.
   
   
2. Pfizer's vaccine was more than 95 percent effective at preventing COVID-19 infection, according to a study published May 5 in The Lancet.
   
   The study was based on more than 230,000 COVID-19 infections in Israel between Jan. 24 and April 3, a time period during which B.1.1.7 accounted for nearly 95 percent of all the country's COVID-19 cases.
   
   
3. Moderna tested a 50-microgram dose of its COVID-19 vaccine in previously vaccinated individuals. Citing early data from that ongoing clinical trial, Moderna said May 6 the booster shot is effective in preventing infection caused by B.1.351 and P.1, the variant first identified in Brazil.
   
   The drugmaker also tested another booster shot developed specifically to neutralize B.1.351, and found that the specialized booster shot generated higher levels of neutralizing antibodies against the variant than the original booster shot did.