Pfizer, BioNTech Halt US Study of Updated COVID-19 Vaccine

‘This study is not ending as a result of any safety or benefit-risk concerns,’ a spokesperson said.

A pharmacist prepares a Pfizer-BioNTech COVID-19 vaccine in Los Angeles on Oct. 24, 2025. Patrick T. Fallon/AFP via Getty Images

Pfizer and its German partner BioNTech are ending a clinical trial they agreed to run in 2025 when receiving approval from U.S. authorities for their updated COVID-19 immunization.

A BioNTech spokesperson confirmed on April 2 that the companies are halting the trial, which was slated to compare healthy vaccine recipients with placebo controls to evaluate the safety and efficacy of the vaccine.