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.

There was some geographic variation.

The vaccine worked better in the US – 72% effective against moderate to severe Covid-19 – compared with 57% in South Africa, where it was up against an easier-to-spread mutated virus.

“Gambling on one dose was certainly worthwhile,” Dr Mathai Mammen, global research chief for J&J’s Janssen Pharmaceutical unit, told The Associated Press.

It comes as a redacted version of AstraZeneca's contract with the European Union has been published amid a deepening row between the two sides over vaccine supply shortages in the bloc.