The rival Pfizer and Moderna vaccines being used in the U.S. and numerous other countries must be kept frozen, while the J&J shot can last three months in the refrigerator, making it easier to handle. AstraZeneca’s vaccine, widely used in Europe, Britain and Israel, is made similarly and also requires refrigeration but takes two doses.
Johnson & Johnson’s single-dose COVID-19 vaccine safe to use, about 66% effective, FDA says
