Washington, United States. Pfizer and BioNTech have halted a large U.S. trial of their updated COVID-19 vaccine in healthy adults aged 50 to 64, saying enrollment was too low to generate needed data.
Trial halted after low enrollment
In a letter to trial investigators dated March 30 and seen by Reuters, Pfizer said it would stop surveillance for signs of COVID illness for all participants in the study after April 3.
Pfizer said enrollment was closed on March 6 following a review of current epidemiological trends.
Regulatory backdrop and demand
The move comes as COVID vaccine makers face weak U.S. demand for shots and pushback from the U.S. administration.
The U.S. Food and Drug Administration toughened requirements for COVID vaccine use last year, including asking for large, placebo-controlled trials in the 50-64 age group for inclusion in recommendations.
Companies cite inability to meet enrollment target
Pfizer and BioNTech told Reuters they informed the FDA of their intent to halt the study, citing challenges in recruiting enough participants. The target enrollment was roughly 25,000 to 30,000 participants.
The companies said the study was not ending due to safety or benefit-risk concerns, but because slow enrollment would prevent generation of relevant post-marketing data.
Market reaction and FDA personnel change
Shares of Pfizer and U.S.-listed shares of BioNTech rose about half a percent, while Moderna shares were up 2%.
FDA vaccine chief Vinay Prasad, who had pushed for placebo-controlled trials in healthy adults and children, is leaving the agency this month. At a meeting of the FDA’s vaccine advisers last year, some experts warned that requiring large new trials could delay or limit the availability of updated shots for lower-risk groups.
The FDA was not immediately available for comment.
How do you think low trial enrollment could affect future decisions on updated COVID-19 vaccine recommendations?
