Johnson & Johnson’s single-shot vaccine effective, but less than some others

Johnson & Johnson’s long-awaited vaccine appears to protect against COVID-19 with just one shot – not as strong as some two-shot rivals but still potentially helpful for a world in dire need of more doses.

J&J said Friday that in the U.S. and seven other countries, the single-shot vaccine was 66% effective overall at preventing moderate to severe illness, and much more protective — 85% — against the most serious symptoms.

There was some geographic variation. The vaccine worked better in the U.S. — 72% effective against moderate to severe COVID-19 – compared to 57% in South Africa, where it was up against an easier-to-spread mutated virus.