The vaccine’s efficacy was highest in the U.S. and the lowest in South Africa, where a new variant is infecting people.
Johnson and Johnson’s single-shot coronavirus vaccine is 85% effective in preventing severe COVID-19 and 66% effective in preventing moderate to severe disease overall, the company announced on Friday (Jan.29). In a large, phase 3 clinical trial that spanned eight countries and included more than 43,700 participants, Johnson and Johnson’s vaccine proved to be 100% effective against COVID-19 hospitalization and death after 28 days, according to a statement. That means that by 28 days after vaccination, none of the vaccinated participants who were infected with COVID-19 were hospitalized or died. But the level of protection against moderate-to-severe disease varied by country. In the U.S., the vaccine was 72% effective in preventing moderate to severe disease; in Latin America, it was 66% effective; and in South Africa — where a new variant is driving most of the cases — it was 57% effective. Related: COVID-19 vaccines in use and how they work This comes a day after Novavax announced that its coronavirus vaccine also dipped in efficacy from nearly 90% in the U.K. to 50% in a small trial in South Africa, according to The New York Times. Preliminary data also found that both the Pfizer and Moderna vaccines may also be less effective against the South Africa variant, according to NBC News.
