The Johnson and Johnson booster vaccine is found to be 85% effective in preventing serious illness in areas where omicron was dominant, as indicated by a South African trial study on Thursday, 30th December 2021.
The South African Research Council conducted the study on health workers from 15th November to 20th December, 2021, but it has still not been peer-reviewed.
It found the top-up jab to largely protect staff in a country where the highly transmissible strain is now behind most Covid cases.
Around half a million South African health staff have received Johnson jabs as part of clinical trials.
An earlier South African study in December found the Pfize/BioNTech vaccine to be less effective overall against Omicron, but still prevented hospital admissions by up to 70%, accordingly.