Johnson & Johnson said Tuesday that Phase 3 studies show that a booster shot of its COVID-19 vaccine increases protection against moderate cases of the virus to 94% in the U.S.
Worldwide, J&J said booster shots made the vaccine 75% effective against moderate cases of the virus, and the company said booster shots were 100% effective in preventing severe cases of COVID-19.
The company also said that when the booster shot was delivered two months after the first shot, antibody levels rose to four to six times higher than observed after the single shot.
"Our single-shot vaccine generates strong immune responses and long-lasting immune memory. And, when a booster of the Johnson & Johnson COVID-19 vaccine is given, the strength of protection against COVID-19 further increases," Dr. Mathai Mammen, Johnson & Johnson's global head of research and development, said in a press release.
During the Phase 3 trials, officials administered the booster shot 56 days after subjects received their first vaccine injection. Johnson & Johnson is the only single-dose vaccine approved for use in the U.S.
J&J is also the only COVID-19 vaccine approved for use that does not employ mRNA technology.
A key panel recommended last week that all Americans aged 65 and older or those who are at risk for severe infection who received the Pfizer vaccine seek out a booster shot eight months after their initial dose. Officials will next weigh approval of booster shots from Moderna, the other mRNA vaccine, and the White House has hinted that it will likely recommend J&J boosters in the future.
J&J also said Tuesday that real-world data showed that its COVID-19 vaccine was 79% effective against COVID-19 infection and 81% effective in preventing hospitalization.
"There was no evidence of reduced effectiveness over the study duration, including when the delta variant became dominant in the U.S.," the company said in its press release.