In a newly released document, analysis from the U.S. Food and Drug Administration (FDA) questions the sensitivity of a test used by Johnson & Johnson to make a case for COVID-19 booster shots. Pointedly, the analysis questioned the amount of time given to analyze trial data.

The agency’s analysis follows a report released on Tuesday, in which Johnson & Johnson argued in favor of a booster, presenting data from a number of trials.

“A booster dose is recommended at 6 months or later, based on the strength of the immune responses,” the company wrote.

But on Wednesday, the F.D.A. said that the test used by the company to measure the immune response of a six-month-boost — known as a psVNA assay — is not sensitive enough for the task. The agency also questioned whether the increase in immune response was as big as the data suggested.

“It is likely that the results seen are due to the low sensitivity of the psVNA assay used,” the F.D.A. stated in its report. Regulators warned that it was difficult to compare results from the company’s six-month and two-month booster studies as a result.

Read the article in its entirety at The New York Times.