J&J Says Second Dose of Their COVID Vaccine Boosts Protection

A second dose of Johnson & Johnson's COVID-19 vaccine given 2 months after the standard one-dose regimen was 94% effective against moderate to severe disease in the U.S., the manufacturer said in topline data released on Tuesday.

However, the confidence interval was wide, with one case in the vaccine arm and 14 in the placebo arm (95% CI 58%-100%).

Globally, the two-dose regimen resulted in 75% efficacy against moderate to severe disease (95% CI 55%-87%), with 14 cases in the vaccine arm and 52 in the placebo arm, according to data from the international ENSEMBLE 2 study.

The additional dose also had 100% protection against severe or critical cases of COVID-19 at least 14 days after the second shot, albeit with an even wider confidence interval (95% CI 33%-100%). There were no cases of severe/critical COVID in the vaccine arm and eight in the placebo arm.

"We now have generated evidence that a booster shot further increases protection against COVID-19 and is expected to extend the duration of protection significantly," said Johnson & Johnson's chief scientific officer, Paul Stoffels, MD, in a statement.

ENSEMBLE 2 is a randomized phase III trial comprised of 31,836 adults ages 18 and up, though it is unclear whether the efficacy numbers reflect the full data set. Johnson & Johnson did not provide the total number of participants in the press release. The second dose was given 56 days after the first.

Median follow-up after the second dose was 36 days, and 29% of participants had at least 2 months of follow-up after their second shot, Johnson & Johnson said.

The company also provided immunogenicity data, which found that when a booster shot was given at 6 months, antibody levels rose to 12-fold higher a month later, irrespective of age.

Johnson & Johnson said it plans to submit these data to the FDA, as well as to peer-reviewed journals for publication. The one-dose viral vector vaccine is currently under emergency use authorization for adults 18 and up.

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