A preliminary South African government study published on Thursday showed that a booster of the Johnson & Johnson Covid vaccine was 85 percent effective in preventing hospitalization from the Omicron variant, a finding that helps revive the reputation of the shot.
The South African Medical Research Council compared 69,000 healthcare professionals who received two doses of the vaccine, based on viral vector technology, with a group of people who were unvaccinated.
When a booster shot was given six to nine months after the first dose, the vaccine’s effectiveness against hospitalization increased over time, from 63 percent 0-13 days to 85 percent one to two months after boost.
The result was also hailed by the company. In a statement, J&J researcher Mathai Mammen said it showed that the vaccine “remains strong and stable over time, including against circulating variants such as Omicron and Delta.”
Africa’s hardest hit country, South Africa, has registered more than 3.4 million cases and 90,000 deaths since the beginning of the pandemic.
A previous South African study in December showed that two doses of the Pfizer-BioNTech vaccine prevented hospitalizations by up to 70 percent. The results for three doses of that vaccine are not yet known.
Preliminary laboratory studies had also shown that the J&J vaccine triggers fewer neutralizing antibodies – Y-shaped proteins that block infection – against the highly mutated Omicron variant compared to mRNA vaccines, and it was suggested that it would be less effective in the real life too.
A separate, small analysis conducted by Beth Israel Deaconess Medical Center in Boston of 65 people found that a J&J booster on top of two doses of the Pfizer Covid vaccine could provide greater protection than three doses of the Pfizer vaccine.
Boost with the J&J vaccine also provoked a strong increase in “killer T cells”.
Overall, the data may mean that mix-and-match boosting could provide stronger protection than continuing with the same vaccine, but the long-term durability of both strategies requires further investigation, J&J said.