The study has not yet been peer reviewed.
A booster dose from Johnson & Johnson (J&J) makes the vaccine 85% effective in preventing severe cases of COVID-19 versus omicron, according to a study conducted in South Africa, where that variant is dominant.
“The efficacy of the vaccine against hospitalizations increases after the injection of the booster dose,” reaching 85% in the first and second months after that second injection, according to a study published Thursday on the pre-publication site medRxiv.
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The study, which has not yet been peer-reviewed, was conducted by the South African Medical Research Council (SAMRC) on healthcare workers from November 15 to December 20.
About half a million South African health workers had previously received a dose of J & J’s vaccine in clinical trials, and some of them received a booster dose six to nine months after the first injection.
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The efficacy rate of the omicron booster dose was determined by comparing a group of 69,000 health workers who had received it with unvaccinated individuals in the nine provinces of the country.
Protection against eventual hospitalization increased over time, from 63% between zero and thirteen days after the booster injection, to 85% between one and two months later.
Earlier in December, another study carried out in South Africa showed that the vaccine from the American laboratory Pfizer was 70% protective against severe cases of the disease caused by omicron, but with two doses. Efficacy results for Pfizer’s three-dose vaccine have not yet been published.
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On the other hand, Johnson & Johnson reported the results of another study, conducted with several dozen people who had been vaccinated with Pfizer, to compare the effect of a booster dose of J&J with a third dose of Pfizer.
Two weeks after the third injection, the Pfizer booster produced more omicron antibodies than the J&J booster.
But four weeks later, the antibodies in the Pfizer booster dose were decreasing and only multiplied by 17, while those of J&J continued to increase, until multiplying by 41. (I)
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