2nd dose of J&J vaccine boosts protection against moderate to severe COVID-19 to 94% in US study, company says

• Johnson & Johnson said a second dose of its COVID-19 vaccine was highly effective in a study.
• Two doses were 94% effective against moderate to severe COVID-19 in US study, it said.
• The company cited data from an unpublished study that hasn't been scrutinized by other experts.

Johnson & Johnson on Tuesday said a second dose of its COVID-19 vaccine was highly effective against moderate to severe COVID-19.

The company said in a press release, citing its own studies, that two doses provided:

• 94% protection against moderate to severe COVID-19 infection in US study;
• 74% protection against moderate to severe COVID-19 infection globally;
• 100% protection against severe COVID-19 at least 14 days after the second shot.

The second dose was administered about two months after the first dose, the company said. For context, Moderna's COVID-19 vaccine was given 28 days apart and Pfizer-BioNTech's 21 days apart in trials. There's some evidence that those two shots have worked better in countries, such as the UK, that delayed the second dose.

The J&J figures are based on a 30,000-patient study, called Ensemble 2, in which a second dose was given to volunteers 56 days apart, STAT News reported.

To get the top-line figures, J&J said 14 people who received two doses caught moderate to severe COVID-19, compared with 52 people who got the placebo. No one got severe or "critical" COVID-19, the company said.

The data hasn't yet been published or scrutinized by experts in a peer review.

Unlike its single-dose shot, a second dose of J&J's vaccine isn't authorized by the Food and Drug Administration.

A recent observational study from the Centers for Disease Control and Prevention of patients with no immunocompromising conditions at 21 US hospitals estimated that a single shot of the J&J vaccine reduced the risk of hospitalization from COVID-19 by 71%. It estimated two doses of Moderna's and Pfizer-BioNTech's shots reduced the risk by 93% and 88%.