Johnson & Johnson's single-shot vaccine is 66 percent effective in preventing moderate to severe COVID-19 cases, the drugmaker announced Jan. 29.
The announcement is based on data from a phase 3 clinical trial that took place in the U.S., Latin America and South Africa. The trial enrolled 43,783 participants, 468 of which showed symptomatic cases of COVID-19.
Data analysis showed the vaccine was 66 percent effective overall in preventing moderate to severe COVID-19 cases 28 days after participants received their shot. The earliest onset of protection was observed just 14 days after receiving the shot.
The protection data differed among the different regions included in the trial, as each region houses different variants of the novel coronavirus. The variant discovered in South Africa, B.1.351, is especially infectious.
Twenty-eight days after vaccination, protection against moderate to severe COVID-19 cases was 72 percent in the U.S., 66 percent in Latin America and 57 percent in South Africa.
Across all regions, data analysis found the vaccine to be 85 percent effective in preventing severe COVID-19 cases 28 days after vaccination. The analysis also found the vaccine showed complete protection against COVID-related hospitalization and death.
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