Pfizer Inc. and its partner BioNTech announced that recruitment for a large U.S. trial of their updated COVID‑19 vaccine in healthy adults aged 50 to 64 has been stopped. The study, which aimed to enroll between 25,000 and 30,000 participants, closed enrollment on March 6 2026 after a review of epidemiological trends showed insufficient enrollment to generate the required data.
The halt reflects the FDA’s current requirement for large, placebo‑controlled trials in the 50‑64 age group and the broader decline in demand for COVID‑19 boosters. CDC data indicate that only about 18 % of Americans received a COVID booster during the 2025‑26 season, underscoring the challenge of recruiting participants for a study that relies on a shrinking target population.
Pfizer and BioNTech stated that the decision was driven solely by slow enrollment and not by any safety or benefit‑risk concerns. “This study is not ending as a result of any safety or benefit‑risk concerns. We intend to stop the study due to slow enrollment and therefore the inability to generate relevant post‑marketing data,” the companies said. CEO Albert Bourla added that the firm had delivered solid performance in 2025 and is refocusing resources on high‑growth areas.
The trial pause signals a strategic shift away from expanding Pfizer’s COVID‑19 vaccine portfolio. The company’s 2025 earnings report showed a year‑over‑year decline in COVID product revenues, and its 2026 guidance projects only about $5 billion in revenue from COVID products—significantly lower than pandemic highs. In contrast, Pfizer is accelerating investments in oncology and obesity, highlighted by the proposed acquisition of Metsera for $4.9 billion and the launch of new obesity‑focused injectables.
Investors reacted mildly to the announcement, with the market’s response remaining muted. The news is part of a broader industry trend of declining demand for COVID‑19 vaccines and illustrates the regulatory and commercial headwinds that Pfizer faces as it reallocates resources to its non‑COVID pipeline.
The halt of the trial underscores the challenges Pfizer faces in maintaining a COVID‑19 revenue stream while pursuing growth in oncology and obesity. It also reflects the broader shift in the pharmaceutical industry toward normalizing pandemic‑era products and focusing on long‑term, high‑margin opportunities.
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