Agency: Researchers have found that a second dose of Johnson & Johnson’s vaccine substantially increased its protection against Covid-19, the company announced Tuesday.
In a clinical trial, the second dose delivered 94 percent efficacy against mild to severe Covid-19 in the U.S., up from 74 percent conferred with a single shot, the company reported. And two shots showed 100 percent efficacy against severe disease, although that estimate had a wide range of uncertainty.
The data, presented in a news release, has been submitted to U.S. drug regulators. The one-dose J. & J. vaccine, which can be easily stored, has been authorized for use in 65 countries worldwide.