Pfizer Shares Available Analyses of Myocarditis and COVID-19 Vaccines

Pfizer Shares Available Analyses of Myocarditis and COVID-19 Vaccines

NEW YORK, Thursday, September 15, 2025 - Pfizer Inc. (NYSE: PFE) today posted publicly available COVID-19 data from global analyses of myocarditis, further representing its dedication to transparency. The extensive and growing body of scientific evidence has also been presented in scientific forums and published in peer-reviewed publications, and Pfizer has posted these myocarditis data in Pfizer's COVID-19 updates and research hub. It provides the following findings:

• Comirnaty, the mRNA vaccine developed by Pfizer-BioNTech, demonstrated very high effectiveness (around 95%) against SARS-CoV-2 infection in early clinical trials.¹ During the recent seasons (2023-2024 and 2024-2025), according to updated CDC data, the COVID-19 vaccines continued to provide additional protection against important clinical outcomes such as hospitalizations, critical illness and deaths, even though effectiveness waned over time.²
• Myocarditis is a recognized risk following vaccination with Comirnaty. It is listed in the prescribing information (USPI) for Comirnaty in Warnings and Precautions and Adverse Reactions sections.³
• Myocarditis following COVID-19 vaccination occurs very rarely as indicated by the results of multiple large pharmaco-epidemiological studies in the United States, France, Nordic Countries, and the United Kingdom, and a meta-analysis.^4,5,6,7,8
• The highest risk of developing myocarditis has been identified in young males within 14 days post-vaccination after the second dose of the primary series of vaccination with an mRNA vaccine.⁹ Furthermore, analyses of data from the U.S. Centers for Disease Control and Prevention (CDC) from the Vaccine Adverse Event Reporting System (VAERS) indicate that myocarditis after a booster vaccine dose is less common than after the second dose of the primary series.¹⁰
• Several important studies have reported on the potential outcomes of myocarditis following COVID-19 infection and vaccination. A systematic review and meta-analysis found that the risk of myocarditis after COVID-19 infection is approximately 42 times higher than the risk after COVID-19 vaccination.¹¹
• When comparing the clinical course of COVID-19 vaccine associated myocarditis with myocarditis due to other causes, studies have suggested more favorable outcomes in COVID-19 vaccine associated myocarditis. One of the largest studies to date with long-term follow-up, a French cohort study based on the French National Health Data System covering all individuals aged 12 to 49 years hospitalized for myocarditis, found that patients with post-COVID-19 mRNA vaccination myocarditis had lower frequency of cardiovascular complications than those with conventional myocarditis at 18 months¹². Analyses of over 42 million vaccinations in England found that the risk of hospital admission or death from myocarditis is greater after COVID-19 infection than after COVID-19 vaccination and remains modest after sequential doses of BNT162b2 mRNA vaccine.⁷
• A separate study funded by the U.S. Food and Drug Administration (FDA), designed to study cases of myocarditis after vaccination, found that mid-term clinical outcomes of 333 individuals with COVID-19 vaccine-associated myocarditis at a median follow-up of 178 days were reassuring, with no reported cardiac related deaths or need for heart transplantations.¹³ A recent prospective study from Australia, recruiting 256 individuals with COVID-19 vaccine associated myocarditis and a longer follow-up of 18 months, reported low hospitalization rates, no deaths, with additional improvements of health-related quality of life over time.¹⁴
• Detailed data have previously been shared with regulators globally and are reflected in the current COVID-19 vaccine label.³

"The ongoing monitoring of the safety of our vaccines is always a priority, and we intend to continue to share the data in an accessible, simple manner," said Chris Boshoff, MD, PhD, Chief Scientific Officer and President, Research and Development at Pfizer. "While COVID-19 infection may pose significant risks, we remain dedicated to closely monitoring potential concerns. Our commitment to rigorous safety protocols and open communication ensures we maintain the confidence of patients, health authorities, and the public at large."

Myocarditis is a very rare adverse event and can be challenging to study; therefore, Pfizer regularly reviews available literature, including the data from clinical studies and real-world evidence studies. All data generated from Pfizer's ongoing studies have been and will continue to be shared with regulators and the public in a timely way.

About Pfizer: Breakthroughs That Change Patients' LivesAt Pfizer, we apply science and our global resources to bring therapies to people that extend and significantly improve their lives. We strive to set the standard for quality, safety and value in the discovery, development and manufacture of health care products, including innovative medicines and vaccines. Every day, Pfizer colleagues work across developed and emerging markets to advance wellness, prevention, treatments and cures that challenge the most feared diseases of our time. Consistent with our responsibility as one of the world's premier innovative biopharmaceutical companies, we collaborate with health care providers, governments and local communities to support and expand access to reliable, affordable health care around the world. For 175 years, we have worked to make a difference for all who rely on us. We routinely post information that may be important to investors on our website at https://www.Pfizer.com. In addition, to learn more, please visit us on https://www.Pfizer.com and follow us on X at @Pfizer and @Pfizer News, LinkedIn, YouTube and like us on Facebook at Facebook.com/Pfizer.

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1 Polack FP, Thomas SJ, Kitchin N, et al. Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine. N Engl J Med 2020; 383(27): 2603-15. https://pubmed.ncbi.nlm.nih.gov/33301246/2 Centers for Disease Control and Prevention. Updates to COVID-19 vaccine effectiveness. COVID-19 session (June 25, 2025). Last accessed September 9, 2025. https://www.cdc.gov/acip/downloads/slides-2025-06-25-26/03-MacNeil-COVID-508.pdf.3 U.S. Food and Drug Administration. COMIRNATY. Last accessed September 9, 2025. https://www.fda.gov/vaccines-blood-biologics/comirnaty.4 Block JP, Boehmer TK, Forrest CB, et al. Cardiac Complications After SARS-CoV-2 Infection and mRNA COVID-19 Vaccination - PCORnet, United States, January 2021-January 2022. MMWR Morb Mortal Wkly Rep 2022; 71(14): 517-23. https://pubmed.ncbi.nlm.nih.gov/35389977/5 Le Vu S, Bertrand M, Jabagi M-J, et al. Age and sex-specific risks of myocarditis and pericarditis following Covid-19 messenger RNA vaccines. Nature Communications 2022; 13(1): 3633. https://pubmed.ncbi.nlm.nih.gov/35752614/6 Karlstad Ø, Hovi P, Husby A, et al. SARS-CoV-2 Vaccination and Myocarditis in a Nordic Cohort Study of 23 Million Residents. JAMA Cardiology 2022; 7(6): 600-12. https://pubmed.ncbi.nlm.nih.gov/35442390/7 Patone M, Mei XW, Handunnetthi L, et al. Risk of Myocarditis After Sequential Doses of COVID-19 Vaccine and SARS-CoV-2 Infection by Age and Sex. Circulation 2022; 146(10): 743-54. https://pubmed.ncbi.nlm.nih.gov/35993236/8 Ling RR, Ramanathan K, Tan FL, et al. Myopericarditis following COVID-19 vaccination and non-COVID-19 vaccination: a systematic review and meta-analysis. Lancet Respir Med 2022; 10(7): 679-88. https://pmc.ncbi.nlm.nih.gov/articles/PMC9000914/9 Buoninfante A, Andeweg A, Genov G, Cavaleri M. Myocarditis associated with COVID-19 vaccination. NPJ Vaccines 2024; 9(1): 122. https://pubmed.ncbi.nlm.nih.gov/38942751/10 Kuehn BM. Myocarditis Adverse Event Less Common After COVID-19 Vaccine Booster. JAMA 2022; 327(14): 1324-. https://pubmed.ncbi.nlm.nih.gov/35412558/11 Choi Y, Lee JS, Choe YJ, et al. Myocarditis and Pericarditis are Temporally Associated with BNT162b2 COVID-19 Vaccine in Adolescents: A Systematic Review and Meta-analysis. Pediatr Cardiol 2024. https://pubmed.ncbi.nlm.nih.gov/39404761/12 Semenzato L, Le Vu S, Botton J, et al. Long-Term Prognosis of Patients With Myocarditis Attributed to COVID-19 mRNA Vaccination, SARS-CoV-2 Infection, or Conventional Etiologies. JAMA 2024; 332(16): 1367-77. https://pubmed.ncbi.nlm.nih.gov/39186694/13 Jain SS, Anderson SA, Steele JM, et al. Cardiac manifestations and outcomes of COVID-19 vaccine-associated myocarditis in the young in the USA: longitudinal results from the Myocarditis After COVID Vaccination (MACiV) multicenter study. EClinicalMedicine 2024; 76: 102809. https://pubmed.ncbi.nlm.nih.gov/39290640/14 Deng L, Van Eldik A, O'Moore M, et al. Surveillance and follow up outcomes of myocarditis after mRNA COVID-19 vaccination in Australia. npj Vaccines 2025; 10(1): 155. https://pubmed.ncbi.nlm.nih.gov/40670372/

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