A top U.S. medical adviser during the Trump and Biden administrations told a woman in early 2020 that masks one buys from drug stores had little effectiveness against the virus that causes COVID-19. “The typical mask you buy in the drug store is not really effective in keeping out virus, which is small enough to pass through the material,” Dr. Anthony Fauci, the longtime head of the National Institute of Allergy and Infectious Diseases, told the woman in an email dated Feb. 5, 2020.