Exclusive: Pfizer, BioNTech halt US COVID vaccine study after recruitment struggles https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-biontech-halt-us-covid-vaccine-study-after-recruitment-struggles-2026-04-01/?taid=69cd76f19654f600013048c9 https://www.reuters.com/business/healthcare-pharmaceuticals/pfizer-biontech-halt-us-covid-vaccine-study-after-recruitment-struggles-2026-04-01/?taid=69cd76f19654f600013048c9
