JOHANNESBURG: A Johnson and Johnson COVID-19 vaccine booster shot is 85% effective in protecting against being hospitalised by the Omicron variant for 1-2 months after it is received, the head of South Africa's Medical Research Council (SAMRC) said on Friday.

Glenda Grey presented the findings of a SAMRC study at a South African health ministry briefing on the COVID-19 fourth wave, which has been driven by the new variant.

"We saw an 85% vaccine effectiveness and we saw that this kind of vaccine effectiveness is maintained for up to two months," she said. We are very happy to report very high levels of vaccine effectiveness against Omicron."

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The study looked at hospitalisations of healthcare workers infected with 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.