The vaccine already is being used in South Africa and the company has applied to the European Union and the World Health Organization for authorization.
Trials of the vaccine in other countries have shown less effectiveness – 66% in Latin America and 57% in South Africa, 28 days after the shots – likely because of variants of the virus circulating in those countries.
The same variants also are circulating in the U.S., but not yet in very high numbers, so the vaccine is expected to be useful here, particularly because it only requires one dose.
Although the J&J vaccine appears less effective than ones from Pfizer-BioNTech and Moderna, it's hard to make direct comparisons, experts say, because those trials were conducted months earlier, at a different point in the pandemic and when there were fewer known variants.
The J&J vaccine was shown to be 85% effective in preventing the most severe disease across all regions studied 28 days after the shot and proved more effective over time, with no cases of severe disease reported after day 49 among those who were vaccinated. The company defined severe disease as respiratory failure, shock, organ failure, or the need for treatment in a hospital intensive care unit.
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