The head of South Africa's Medical Research Council (SAMRC), Glenda Gray, has said that a study has shown that Johnson and Johnson (NYSE:JNJ) COVID-19 vaccine booster shot is 85% effective in protecting against being hospitalised by the Omicron variant for one to two months after it is received, Reuters news agency reported on Friday.

The SAMRC study involved 477,234 healthcare workers, all of them vaccinated with the J&J shot, of whom 236,000, or approximately half, had received the J&J booster shot.

It looked at hospitalisations among those healthcare workers who had been infected during the fourth wave and found that the booster shot reduced hospitalisations by 63% in the first two weeks after the booster, going up to 85% after that for between one and two months.

Among the participants in the study, there were also about 30,000 breakthrough infections during the Omicron wave, compared with only around 11,000 each in the previous waves driven by the Delta and Beta variants.

In addition, the study highlighted that those infected with HIV were more vulnerable to being hospitalised with Omicron.