A clinical trial in South Africa found that a Johnson & Johnson booster shot greatly reduced the risk of hospitalization.
The study found that two shots of the vaccine reduced the risk of hospitalization from Omicron by about 85%. Two shots of the Pfizer-BioNTech vaccine reduced the risk of hospitalization by about 70 percent according to a study in South Africa.
The Centers for Disease Control and Prevention recommends that other vaccines be used instead of the Johnson & Johnson vaccine. The C.D.C. raised concerns about the Johnson & Johnson vaccine.
The authors of the new study said that the results were important for vaccination efforts in Africa, where the Johnson & Johnson vaccine is a mainstay of Covid public health efforts. A second dose of the vaccine could prevent a surge of hospitalizations as the continent braces for a wave of Omicron cases.
When Delta was still the dominant variant worldwide, Johnson & Johnson found that a second dose of its vaccine increased its efficacy after eight weeks. In the U.S. arm of the trial, efficacy against mild to severe Covid-19 rose to 94 percent, compared with 74 percent for one shot. The vaccine protected volunteers against severe disease in 10 countries.
South Africa launched a trial in November of health care workers who had already received one dose of the vaccine. The researchers running the trial began tracking how boosted health care workers did against the Omicron variant, finding that it worked well.
This result was somewhat surprising, given that people who had received one dose of the vaccine failed to block Omicron from infecting cells in laboratory experiments.
It is possible that the booster shots raised the levels of the protective antibodies. The immune system is made up of many parts, including the body's immune system.
Immune cells help fight Covid. In a study posted online on Tuesday, South African researchers found that the immune cells taken from people who received Johnson & Johnson vaccines recognized Omicron-infected cells almost as well as they recognized cells that were not Omicron.
It is possible that Johnson & Johnson booster shots increase the army of immune cells that can wage war on Omicron.
