Johnson & Johnson vaccine 66% effective against moderate to severe Covid-19

The Johnson & Johnson shows vials for a single-dose Covid-19 vaccine. Picture: Cheryl Gerber/Johnson & Johnson via AP)

Johnson & Johnson’s long-awaited vaccine appears to protect against Covid-19 with just one shot – but not as strong as some two-shot rivals.

J&J said on Friday that in the US 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.