Phase 3 Data Confirm Strong Immune Response With Pfizer-BioNTech LP.8.1 COVID-19 Vaccine for 2025–2026 Season

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Pfizer and BioNTech announced topline results from an ongoing Phase 3 clinical trial evaluating their LP.8.1-adapted monovalent COVID-19 vaccine for the 2025–2026 season. The findings, released September 8, 2025, demonstrated a strong immune response in adults aged 65 years and older and in adults aged 18 to 64 with at least one underlying risk factor for severe disease.¹

The open-label trial enrolled 100 participants, including 50 adults ≥65 years and 50 adults aged 18–64 with risk conditions. All participants had previously received a KP.2-adapted vaccine at least 6 months prior to enrollment and had no history of COVID-19 infection or vaccination since that time. Results showed that 14 days after receiving the 30-µg dose of the LP.8.1-adapted vaccine, neutralizing antibody titers against the LP.8.1 sublineage increased at least 4-fold compared with pre-vaccination levels in both age groups.¹

Pfizer reported that the safety profile was consistent with prior studies, with no new safety concerns identified. According to data filed in the US clinical trial registry, participants were recruited across six US sites beginning in early July 2025, with primary data collection completed within two months. The study is expected to conclude in January 2026.¹

The trial was designed to provide additional immunologic data for prescribers during the 2025–2026 vaccination period and does not replace ongoing FDA postmarketing commitments. Pfizer has also agreed to conduct placebo-controlled, postmarketing studies in healthy adults, as well as a study evaluating the persistence of vaccine-derived spike protein antigens in the body, with results expected in 2027.¹

The release of these data follows public discussion about transparency in COVID-19 vaccine research. Last week, Pfizer, Moderna, and Novavax each defended the data supporting their vaccines after public remarks by political leaders questioned their safety and effectiveness.² Pfizer CEO Albert Bourla reiterated the company’s commitment to data transparency in a statement.¹

Pfizer and BioNTech noted that more than 5 billion doses of their COVID-19 vaccine have been distributed worldwide to date. The vaccines, marketed as Comirnaty, are based on BioNTech’s proprietary mRNA technology and have been supported by real-world safety and effectiveness data.¹

Comirnaty is indicated in the US for adults ≥65 years and for individuals aged 5 to 64 years with at least one underlying risk condition that increases the likelihood of severe COVID-19 outcomes.³

1. Pfizer and BioNTech Announce Topline Data Demonstrating Robust Immune Response With Their LP.8.1-Adapted COVID-19 Vaccine 2025-2026 Formula. News release. Pfizer. September 8, 2025. Accessed September 9, 2025. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-topline-data-demonstrating
2. Halsey G. Updated COVID-19 Vaccines Are Approved, But Population Restrictions Concern Experts. Patient Care. August 29, 2025. Accessed September 9, 2025. https://www.patientcareonline.com/view/updated-covid-19-vaccines-are-approved-but-population-restrictions-concern-experts
3. Pfizer and BioNTech’s Comirnaty® receives U.S. FDA approval for adults 65 and older and individuals ages 5 through 64 at increased risk for severe COVID-19. News release. Pfizer. August 27, 2025. Accessed September 9, 2025. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontechs-comirnatyr-receives-us-fda-approval