Pfizer and BioNTech Halt COVID-19 Booster Trial Due to Lack of Willing Participants

WASHINGTON – Pfizer and BioNTech announced on April 2, 2026, that they have terminated their latest COVID-19 booster clinical trial after failing to recruit enough willing volunteers.

The study was designed to evaluate a new monovalent booster targeting currently circulating variants. Despite extensive recruitment efforts, the companies could not meet the minimum enrollment threshold required for statistically valid results. As a result, the trial has been shut down entirely.

This marks the most prominent example yet of major vaccine manufacturers struggling to find participants for updated COVID-19 shots. Earlier attempts by other companies to launch similar booster trials also faced significant delays or scaling back due to low interest.

Public uptake of COVID-19 boosters has collapsed in recent years. CDC data shows that fewer than 10% of eligible adults received the most recent formulation. Participation in new clinical trials has followed the same downward trend, with many Americans citing vaccine fatigue, concerns over repeated dosing, and questions about long-term efficacy as reasons for declining.

The original COVID-19 vaccines were rolled out more than five years ago. While initial doses achieved high uptake, subsequent boosters have seen dramatically lower participation. Real-world data has shown that protection against infection wanes quickly, while the risk of severe outcomes remains concentrated among the elderly and those with multiple comorbidities.

Pfizer and BioNTech did not provide additional details on future plans for their COVID-19 program. The companies stated only that they will “evaluate next steps” but offered no timeline for any new trials.

The shutdown reflects a broader shift in public sentiment five years after the pandemic. Health officials continue to recommend regular boosters for certain high-risk groups, but the difficulty in recruiting trial participants underscores the sharp decline in demand for additional doses.

No immediate comment was issued by the FDA or CDC regarding the trial’s termination. The development comes as the pharmaceutical industry reassesses its long-term COVID-19 vaccine strategy amid waning public interest.