The Johnson & Johnson coronavirus vaccine has been shown to be 66 per cent effective at preventing moderate to severe illness, according to data from a phase-3 clinical trial.
The one-shot vaccine has also been shown to be 85 per cent effective at preventing the most serious symptoms – those that require hospitalisation – after 28 days, and 100 per cent effective at preventing these symptoms after 49 days.
There was some geographic variation in the results, which may have been driven by the different coronavirus strains emerging across the world. Trials in the US found the vaccine to be 72 per cent effective against moderate to severe COVID-19 while studies in Latin America and South Africa – where more contagious strains have emerged – found the vaccine to be only 66 per cent and 57 per cent effective, respectively.
