A Johnson & Johnson booster injection provided strong protection against the Omicron variant, significantly reducing the risk of hospitalization, according to a clinical trial in South Africa.
The study, which compared more than 69,000 fortified health professionals with a corresponding group of unvaccinated South Africans, found that two injections of the vaccine reduced the risk of hospitalization from Omicron by about 85 percent. In comparison, another study in South Africa found that two injections of the Pfizer-BioNTech vaccine reduced the risk of hospitalization by about 70 percent.
Although the U.S. Food and Drug Administration has approved the Johnson & Johnson vaccine as a booster injection, the Centers for Disease Control and Prevention recommended giving preference to other vaccines. The CDC expressed concern about rare but life-threatening blood clots associated with the Johnson & Johnson vaccine.
But the authors of the new study, which was published on a preprint server and has not yet been peer-reviewed, said the results were important for vaccination efforts in Africa, where the Johnson & Johnson vaccine is a mainstay of the effort. on public health due to Covid. . As the continent braces for a wave of Omicron cases, a second dose of the vaccine could prevent a wave of hospitalizations.
In another clinical trial that ended in September, when Delta was still the dominant variant worldwide, Johnson & Johnson found that a second dose of its vaccine administered eight weeks after the first significantly increased its efficacy. In the US arm of the study, efficacy against mild to severe Covid-19 increased to 94 percent, compared to 74 percent for a single injection. At trial sites in 10 countries, the vaccine protected all volunteers from serious illness.
Those results prompted South Africa to start a trial in November among health professionals who had already received one dose of the vaccine six to nine months earlier. When the Omicron variant started showing up in South Africa in late November, the researchers leading the trial began monitoring how health professionals were doing against the variant, and found that it worked well.
This result was somewhat surprising, since antibodies taken from people who had received one dose of the vaccine failed to block Omicron from infecting cells in lab experiments.
It is possible that the booster injections increased the antibodies to protective levels. And while antibodies help the body fight off infection, they’re just one of many parts of the immune system.
Certain immune cells help fight Covid by attacking virus-infected cells. In a study posted online Tuesday, South African researchers found that immune cells taken from people who had received Johnson & Johnson vaccines recognized Omicron-infected cells almost as well as cells infected with other variants.
It is possible that Johnson & Johnson booster shots will not only raise antibodies but also increase the army of immune cells that can wage war against Omicron.