Pfizer-BioNTech LP.8.1-Adapted mRNA COVID-19 Vaccine Shows Robust Immune Response in Phase 3 Trial

NEW YORK & MAINZ, Germany- September 08, 2025— Pfizer Inc. and BioNTech SE announced on Monday, September 8, 2025, that their updated COVID-19 mRNA booster vaccine, the LP.8.1-adapted monovalent COMIRNATY® 2025-2026 Formula, has demonstrated a strong immune response in a Phase 3 clinical trial cohort. The new data provides a key piece of evidence supporting the recently approved mRNA shot.

The study, which included 100 participants—50 adults aged 65 and older and 50 adults aged 18 to 64 with at least one underlying risk condition—showed that the mRNA booster led to at least a four-fold increase in neutralizing antibody titers against the currently circulating LP.8.1 sublineage of SARS-CoV-2. This occurred 14 days after vaccination and in individuals who had previously received the KP.2-adapted mRNA vaccine at least six months prior.

The companies reported that the safety profile of the mRNA vaccine was consistent with previous studies, and no new safety concerns were identified. These clinical findings reinforce the pre-clinical data that supported the U.S. Food and Drug Administration (FDA) approval of the LP.8.1-adapted mRNA vaccine, which demonstrated improved immune responses against multiple circulating SARS-CoV-2 sublineages.

Pfizer and BioNTech, whose COVID-19 vaccines are based on BioNTech’s proprietary mRNA technology, have submitted these new data to the FDA. To date, over 5 billion doses of their mRNA COVID-19 vaccine have been distributed globally.