Pfizer and BioNTech Pause Covid Vaccine Study Following Low Enrollment Totals
April 3, 2026
Source: Pharm Exec
Photo / Image Source: Unsplash,
Key Takeaways
Pfizer and BioNTech stopped COVID-19 illness surveillance after April 3 following enrollment closure, citing inadequate recruitment to meet FDA-required post-marketing evidence thresholds.
Restrictive eligibility excluding prevalent comorbidities (e.g., hypertension, diabetes) caused >80% pre-screen failures, making accrual of 25,000–30,000 healthy adults aged 50–64 infeasible.
No full FDA approval exists for healthy 50–64-year-olds; without large placebo-controlled data, expanding recommendations/authorization for this cohort is now uncertain.
Reduced booster uptake and heightened FDA evidentiary requirements in lower-risk groups are converging with political headwinds, complicating COVID vaccine lifecycle strategies.
Moderna’s parallel 30,000-participant U.S. trial remains active but is also experiencing recruitment friction, with projected completion in 2027.
Pfizer and BioNTech halted a large U.S. clinical trial targeting healthy adults aged 50 to 64 after enrollment shortfalls made it impossible to generate the post-marketing data the FDA required.
Both company’s say the enrollment was too low to collect the required data.Stock.Adobe.com
Pfizer and BioNTech halted a large U.S. clinical trial of their updated Covid-19 vaccine in healthy adults aged 50 to 64.
Both companies say enrollment shortfalls made it impossible to generate the data required by FDA to potentially expand the vaccine's recommended use to that age group.
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