Pfizer and BioNTech Report Data for Adapted COVID-19 Vaccine

Pfizer and BioNTech announced on Monday, September 8, 2025, the release of topline results from an ongoing Phase 3 clinical trial evaluating their LP.8.1-adapted COVID-19 vaccine, formula 2025-2026. The study assessed the safety, tolerability, and immunogenicity of the vaccine in adults aged 65 and older, and in adults aged 18 through 64 with at least one risk condition for severe COVID-19.

Preliminary findings indicated that the vaccine elicited a robust neutralizing antibody response against the LP.8.1 sublineage of SARS-CoV-2. Fourteen days post-vaccination, LP.8.1-neutralizing antibody titers, on average, increased at least fourfold compared to pre-vaccination levels in both age groups. The vaccine's safety profile was consistent with previous studies, with no new safety concerns identified.

The open-label Phase 3 trial cohort included a total of 100 participants: 50 adults aged 65 and older and 50 adults aged 18-64 with at least one underlying risk condition. All participants had received the KP.2-adapted COVID-19 vaccine at least six months prior to enrollment and had not received any other COVID-19 vaccine or had COVID-19 since their KP.2 vaccination.

This study was conducted to provide additional information on the vaccine's immunological effects and reinforces the FDA's recent approval of the 2025-2026 formula, which demonstrated improved immune responses against multiple circulating SARS-CoV-2 sublineages. Pfizer and BioNTech have submitted these data to the FDA. The companies have distributed a total of 5 billion doses of their COVID-19 vaccine globally.