In an attempt to ensure the effectiveness of their COVID-19 vaccines against new variants of the novel coronavirus, both Pfizer and Moderna are testing a third booster shot of their respective two-dose vaccines. On February 25, Pfizer announced that it is studying a third booster dose in some people who received their first dose of the vaccine more than six months ago. The company specifically stated that emerging and future variants of SARS-CoV-2, the coronavirus that causes COVID-19, were the reason for the study. Pfizer also said that it is exploring the possibility of a new, “variant-specific vaccine” that would target B.1.351 (the highly infectious South African variant). To read the full story.