This is an update of an article originally published on November 24, 2020. New data is coming in on the efficacy of the various vaccines, and the Pfizer-BioNTech and Moderna vaccines are being distributed in the U.S. and other countries.
This article is part of a series of explainers on vaccine development and distribution. Learn more about vaccines – from how they work and how they’re made to ensuring safety and equitable access – in WHO’s Vaccines Explained series.
