The boosting dose of the single dose vaccine against COVID-19 of Johnson & Johnson was 84% effective in preventing hospitalization of healthcare workers in South Africa who became infected with the coronavirus as the Omicron variant spread, researchers said today.
The fact-finding study, which has not yet been evaluated by peers, involves a second dose of the J&J vaccine given to 69.092 health workers between November 15 and December 20.
The initial vaccination has been shown to offer considerably reduced protection against the Omicron variant, which is spreading rapidly in many countries having first been identified in late November in South Africa and Hong Kong.
However, many studies have suggested that a booster dose provides significant protection against severe disease from this variant.
This South African study showed that the effectiveness of the J&J vaccine in preventing hospitalization increased from 63% shortly after the booster dose to 84% after 14 days.
Its effectiveness reached 85% one to two months after the booster dose.
"She confirms that the vaccines against her COVID-19 "They are still effective for the purpose for which they were designed to protect people from serious illness and death," said Linda-Gail Becker, co-author of the study.
"This is further proof that we have not lost this effectiveness even with a very mutated variant," he added.
According to her, however, the issue of further doses of the J&J vaccine is still not entirely clear.
"What we are saying is that two doses do provide complete protection and I do not think we can conclude that we will need a third or fourth boost."
The researchers said their analysis faced many limitations, including short retest times, which averaged eight days for health workers who had received a booster dose in the previous 13 days or 32 days for those who had received booster dose one or two months earlier and which could distort the overall effectiveness of the vaccine.
Another South African study recently found that a first round of two doses of the Pfizer-BioNTech vaccine was less effective in South Africa in keeping those infected with the virus out of the hospital than the Omicron variant.
Source: RES-EAP