What to Know About Johnson & Johnson’s Single-Dose COVID-19 Vaccine Prevention 3/12/2021 Korin Miller Johnson & Johnson’s single-dose COVID-19 vaccine has been authorized for emergency use by the U.S. Food and Drug Administration. On March 10, President Joe Biden announced his intent to purchase an additional 100 million doses of the Johnson & Johnson vaccine. The Johnson & Johnson vaccine was 85% effective at preventing severe or critical forms of COVID-19 28 days after vaccination and 100% effective at preventing COVID-related deaths in the company’s phase 3 clinical trial. Johnson & Johnson’s COVID-19 vaccine began shipping out to states on March 1 after receiving authorization from the Food and Drug Administration (FDA) on February 27. Unlike its mRNA, two-dose vaccine competitors from Pfizer-BioNTech and Moderna, this one requires just a single dose.