The 2025-26 Pfizer COVID-19 vaccine is about 57% effective against emergency department/urgent care (ED/UC) visits and 54% effective against outpatient visits among adults roughly 4 weeks after vaccination, with considerable uncertainty, according to preliminary estimates published on the preprint server medRxiv.

A team that included researchers from the Providence Veterans Affairs (VA) Healthcare System and Pfizer used a test-negative case-control design to estimate the early vaccine effectiveness (VE) of Pfizer’s BNT162b2 LP.8.1 vaccine against ED/UC and outpatient visits.

Participants were VA patients who had an acute respiratory infection (ARI) and underwent COVID-19 testing from September 10 to November 30, 2025.