As with the many other questions that still remain about the coronavirus, no one is precisely sure of the answer to one of the key questions: how many people will need to be vaccinated to achieve herd immunity—the threshold at which there are enough people immunized that it indirectly protects the rest of the yet-unvaccinated public—and fully end the pandemic. In December, National Institute of Allergy and Infectious Diseases Director Anthony Fauci estimated that the cutoff was at least 75%, and closer to 85%.
