(Reuters) – U.S. Food and Drug Administration scientists said on Wednesday they did not receive enough data in time to do their own analysis of Johnson & Johnson’s application for a booster dose of its COVID-19 vaccine, but the agency’s review of company studies raised some red flags.
Advisers to the FDA will meet on Oct. 15 to assess the risks and benefits of a booster shot of J&J’s vaccine, which is currently given as a single dose.
In its review, FDA scientists repeatedly noted the limitation of small sample sizes of many of the company’s studies.
They noted that data J&J used to support administering a booster six months after the initial shot relied on a test to measure immune response that has not been validated and was possibly not sensitive enough.
That mismatch in assessment tools would make it challenging to make meaningful comparisons with data from the company’s larger two-dose booster trial.
Agency scientists also noted that there were insufficient cases of COVID-19 caused by the Delta variant to estimate how effective the vaccine is against the coronavirus mutation now dominant globally in that larger J&J trial evaluating two doses of the vaccine given nearly two months apart.
U.S. health officials have been under pressure to offer advice on booster doses of the J&J and Moderna COVID-19 vaccines after the White House announced in August it planned to roll out boosters beginning last month for most adults, pending approvals from the FDA and the U.S. Centers for Disease Control and Prevention (CDC).
The FDA and CDC last month signed off on boosters here of the Pfizer Inc and BioNTech SE COVID-19 vaccine for certain high-risk adults, but reviews of the Moderna and J&J shots were delayed until the companies could produce more data.
The FDA on Tuesday released its assessment here of Moderna’s booster application ahead of a meeting of expert advisers on the topic on Thursday. Neither assessment made a recommendation to the panel on whether the data supports use of booster shots.
Independent vaccine experts at the meeting on Friday will hear presentations from the FDA and J&J scientists, and be asked whether company data supports use of a booster dose at least two months after the initial shot. They also will be asked to assess whether a J&J booster given six months after the first shot may result in a more robust immune response.