Pfizer and BioNTech shut down a 25,000–30,000-person COVID-19 vaccine trial on March 6, unable to recruit enough healthy adults to generate the regulatory data the FDA specifically required.
The study targeted adults aged 50 to 64, a group the FDA singled out last May when it announced placebo-controlled trial requirements for that cohort. Neither Comirnaty nor Moderna’s Spikevax carries full approval for this age group — and that approval data was the entire purpose of the trial.
More than 80% of willing participants failed prescreening because of chronic conditions like hypertension or diabetes. Pfizer told investigators on March 30 it won’t continue COVID surveillance past April 3 — effectively pulling the plug.
Moderna’s trial in the same age group isn’t going much better. Four site sources told Reuters that enrollment is struggling there too. Moderna CFO James Mock warned in March that US sales could fall from $1.2 billion to roughly $1 billion in 2026. The forecast followed political and regulatory pressure on mRNA vaccines.
Without this data, neither company can secure full FDA approval for the 50-64 cohort. The FDA’s requirements don’t disappear because a trial can’t fill seats.
Moderna’s resubmitted flu vaccine application is due for an FDA decision in August.
— Sarah Chen