CAPE TOWN— A booster dose of Johnson & Johnson Inc's single-dose COVID-19 vaccine was 84 percent effective at preventing hospitalization in South African health care workers who became infected as the omicron variant spread, researchers said on Thursday.
The real-world study, which has not been peer-reviewed, was based on a second dose of the J&J vaccine administered to 69,092 health-care workers between Nov. 15 and Dec. 20.
An initial course of inoculation has been shown to offer greatly reduced protection against Omicron, particularly against infection. However, several studies have suggested that a booster dose still provides significant protection against severe illness.
The new South African study of the J&J shot showed that the vaccine's effectiveness at preventing hospitalization rose from 63 percent shortly after a booster was administered to 84 percent 14 days later. Effectiveness reached 85 percent at 1 to 2 months post-boost.
Earlier this month, another South African-based study showed that a first round of inoculation with 2 doses of Pfizer-BioNTech's COVID-19 vaccine had been less effective in South Africa at keeping people infected with the virus out of hospital since the omicron variant emerged last month.
The trial has been evaluating the efficacy of the J&J vaccine in the field after it was suspended due to concerns over extremely rare cases of blood clots.
Scientists in South Africa first alerted the World Health Organization that they had detected omicron in late November. The highly-mutated variant has spread quickly in other countries, and is fueling a new wave of infections.