Pfizer, BioNTech’s Comirnaty Shows Strong Immune Response in Phase III Trial for COVID-19

Results from a Phase III trial showed that Comirnaty, Pfizer and BioNTech’s COVID-19 vaccine for the 2025–2026 season, elicited strong immune responses in higher-risk adults. According to the companies, the updated vaccine is expected to play an important role in protecting vulnerable populations during the upcoming season.¹

Phase III Trial Cohort

• The open-label trial cohort evaluated the safety, tolerability, and immunogenicity of Comirnaty in 100 patients aged 65 years and older as well as adults between the ages of 18 and 64 years with at least one underlying risk condition for severe COVID.
• Prior to receiving the vaccine, all patients had received the KP.2-adapted COVID vaccine at least six months prior to the start of enrollment.
• Additionally, patients were required to have not received any other COVID vaccines or have had COVID since the KP.2 vaccination through enrollment in the study.
• Primary endpoints of the trial included the percentage of patients reporting local reactions, percentage of patients reporting systemic events, percentage of patients reporting adverse events (AEs), percentage of patients with serious AEs, and percentage of patients with seroresponse.
• Key secondary endpoints included percentage of patients with seroresponse one month after vaccination, geometric mean titers one month after vaccination, and geometric mean fold rises from before vaccination to one month after vaccination.
• Results showed that the vaccine elicited at least a fourfold increase in neutralizing antibodies against the LP.8.1 sublineage within 14 days of vaccination.
• The safety profile of Comirnaty was reported to be consistent with previous studies and no new safety signals were identified.

AEs

• Pfizer warns that Comirnaty could cause a number of AEs, which include allergic reactions, myocarditis, chest pain, shortness of breath, pounding heart, fainting, persistent fatigue, vomiting, pain in the abdomen, and pale skin.
• Other common allergic AEs include rash, itching, hives, and face swelling.
• Injection site reactions include pain, swelling, redness, and arm pain.
• Common AEs included tiredness, headache, muscle pain, chills, joint pain, fever, nausea, feeling unwell, swollen lymph nodes, decreased appetite, diarrhea, vomiting, and dizziness.^1,2

Regulatory Approvals and CDC Data

• Comirnaty first received FDA approval in August 2021 for patients aged 16 years and older.³
• In July 2022, approval was expanded to include patients aged 12 to 15 years.⁴
• In September 2023, Comirnaty was granted emergency use authorization for patients aged six months through 11 years.⁵
• In August, the FDA approved Comirnaty in patients aged 65 years and older and in patients aged five through 64 years with at least one underlying condition that puts them at high risk for severe outcomes from COVID.⁶
• According to the Centers for Disease Control and Prevention, test positivity for COVID was 10.8% in the United States in the week ending August 30, 2025.
• In the same week, emergency department visits were at 1.6%, up from 1.5% the previous week.
• Deaths were at 0.6%, up from 0.5% the previous week.⁷

Global Distribution and Safety Record

According to Pfizer, close to five billion doses of Comirnaty have been administered to date, with a well-established record of safety and effectiveness supported by extensive real-world use as well as clinical, non-clinical, safety monitoring, and manufacturing data.

The vaccine currently has marketing authorizations in the United States, United Kingdom, European Union, and a number of other countries. Additionally, it has been authorized for emergency use in other markets.¹

References

1. Pfizer and BioNTech Announce Topline Data Demonstrating Robust Immune Response With Their LP.8.1-Adapted COVID-19 Vaccine 2025-2026 Formula. Pfizer. September 8, 2025. Accessed September 8, 2025. https://www.pfizer.com/news/press-release/press-release-detail/pfizer-and-biontech-announce-topline-data-demonstrating
2. A Study to Learn About COVID-19 RNA-Based Variant-Adapted Vaccine Candidate(s) Against SARS-CoV-2 in Adults, Including Those at Higher Risk of Severe COVID-19. Clinicaltrials.gov. Accessed September 8, 2025. https://clinicaltrials.gov/study/NCT07069309?utm_source=chatgpt.com
3. FDA Approves Comirnaty. Drugs.com. August 23, 2021. Accessed September 8, 2025. https://www.drugs.com/newdrugs/fda-approves-comirnaty-pfizer-biontech-covid-19-vaccine-prevent-covid-19-individuals-16-years-older-5633.html
4. Pfizer and BioNTech Announce U.S. FDA Approval of Their COVID-19 Vaccine Comirnaty for Adolescents 12 Through 15 Years of Age. Drugs.com. July 8, 2022. Accessed September 8, 2025. https://www.drugs.com/newdrugs/pfizer-biontech-announce-u-s-fda-approval-their-covid-19-vaccine-comirnaty-adolescents-12-through-5858.html
5. Pfizer and BioNTech Receive U.S. FDA Approval for 2023-2024 COVID-19 Vaccine. Drugs.com. September 11, 2023. Accessed September 8, 2025. https://www.drugs.com/newdrugs/pfizer-biontech-receive-u-s-fda-approval-2023-2024-covid-19-vaccine-6089.html
6. 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. Drugs.com. August 27, 2025. Accessed September 8, 2025. https://www.drugs.com/newdrugs/pfizer-biontech-s-comirnaty-receives-u-s-fda-approval-adults-65-older-individuals-ages-5-through-64-6598.html

Surveillance and Data Analytics. CDC. Accessed September 8, 2025. https://www.cdc.gov/covid/php/surveillance/index.html