Pfizer Inc. and BioNTech said on April 1 their Covid-19 vaccine is around 91 percent effective at preventing the disease, citing updated trial data that included participants inoculated for up to six months.

Pfizer Inc. and BioNTech SE said on March 10 that real-world data from Israel suggests their Covid-19 vaccine is 94 percent effective in preventing asymptomatic infections, meaning it could significantly reduce transmission.

The Covid-19 vaccine from Pfizer Inc. and BioNTech SE was able to neutralize a new variant of the coronavirus spreading rapidly in Brazil, according to a laboratory study published in the New England Journal of Medicine on March 8.

Preliminary data from a study conducted at the University of Oxford indicates that the Covid-19 vaccine developed by AstraZeneca is effective against the Brazilian variant P1, a source with knowledge of the study told Reuters on March 5.

Mayor Bill de Blasio’s chief medical adviser on Feb. 25 downplayed the results of two studies suggesting that a new coronavirus variant found in New York City in November will be more resistant to vaccines now being administered.

Many health experts believe that the Covid-19 vaccine candidate NVX-CoV237 from Novavax offers potential advantages over competitors including Pfizer-BioNTech, Moderna, Johnson & Johnson, and AstraZeneca-Oxford.

Johnson & Johnson’s one-dose Covid-19 vaccine appeared safe and effective in trials, the U.S. Food and Drug Administration said, paving the way for approval for emergency use as soon as Feb. 26.

The U.S. Food and Drug Administration issued new guidance for vaccine makers as the regulatory agency is preparing for the possibility of needing to approve Covid-19 booster shots against variants of the SARS-CoV-2 virus.

South Africa delayed the distribution of the AstraZeneca-University of Oxford Covid-19 vaccine after data suggested it “provides minimal protection” against mild disease from the South African variant.