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Safety of BNT162b2 mRNA COVID-19 Vaccine
Quick Takes
- In this clinical trial emulation, the authors use data from an integrated health care system in Israel to estimate the risks of adverse events related to vaccination with BNT162b2 compared to nonvaccination, and that of SARS-CoV-2 infection compared to noninfection.
- Overall, the relative risks of adverse effects attributed to vaccination were much lower than those of adverse effects attributed to SARS-CoV-2 infection, including myocarditis, pericarditis, and thromboembolism.
- For example, while the BNT162b2 vaccine was associated with an excess risk of myocarditis (1-5 per 100,000 persons), the risk of myocarditis attributed to COVID-19 is significantly higher (11 per 100,000 persons).
Study Questions:
What are the relative risks of vaccine-related adverse events of the BNT162b2 mRNA vaccine (Pfizer–BioNTech) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and how do they compare to the risks of adverse events related to coronavirus disease 2019 (COVID-19)?
Methods:
In this clinical trial emulation, the authors leveraged data repositories from the largest integrated health care organization in Israel to match recipients of the BNT162b2 mRNA vaccine to nonvaccinated participants according to age, sex, sociodemographic, economic, and clinical characteristics. Participants were ≥16 years old. Follow-up was limited to 42 days post-initial vaccination. Data on a wide range of adverse events were collected. A similar analysis was performed matching SARS-CoV-2–infected persons to uninfected persons. The same adverse events were studied in the vaccination and SARS-CoV-2 infection analyses. A matched pair was censored if the initially unvaccinated or uninfected persons became vaccinated or infected, respectively.
Results:
In the vaccination analysis, the vaccinated and control groups each included 884,828 persons (median age of 38 years, 48% women, 36% with ≥1 risk factor for COVID-19). Vaccination was most strongly associated with an elevated risk of myocarditis (risk ratio [RR], 3.24; 95% confidence interval [CI], 1.55-12.44), lymphadenopathy (RR, 2.43; 95% CI, 2.05-2.78), appendicitis (RR, 1.40; 95% CI, 1.02-2.01), and herpes zoster infection (RR, 1.43; 95% CI, 1.20-1.73). A total of 173,106 persons were included in the SARS-CoV-2 infection analysis (median age 36 years, 54% women). SARS-CoV-2 infection was associated with a substantially increased risk of myocarditis (RR, 18.28; 95% CI, 3.95-25.12), acute kidney injury (RR, 14.83; 95% CI, 9.24-28.75), pulmonary embolism (RR, 12.14; 95% CI, 6.89-29.20), and other serious adverse events, including pericarditis, arrhythmia, deep-vein thrombosis, myocardial infarction, intracranial hemorrhage, and thrombocytopenia.
Conclusions:
The relative risks of serious adverse events related to the BNT162b2 vaccine were low and far lower than those related to COVID-19.
Perspective:
This clinical trial emulation confirms recent reports of an increased rate of myocarditis in recipients of BNT162b2 vaccines; albeit much lower than that of patients with COVID-19. This study also confirms that the risks of other feared vaccination-related adverse effects such as thromboembolism (seen with the ChAdOx1 vaccine) were low. It also highlights nicely that the relative risks attributed to a SARS-CoV-2 infection for these same adverse effects are dramatically higher than that of vaccination, an intuitive but important point to make for those reluctant to get vaccinated: The vaccine is much safer than the infection. The study is a bird’s eye view and does not identify specific subgroups at higher risk, among other limitations related to its observational nature, and the inability to directly compare vaccination and infection groups.
Clinical Topics: Arrhythmias and Clinical EP, Cardiovascular Care Team, COVID-19 Hub, Heart Failure and Cardiomyopathies, Pericardial Disease, Prevention, Vascular Medicine, Implantable Devices, SCD/Ventricular Arrhythmias, Atrial Fibrillation/Supraventricular Arrhythmias
Keywords: Acute Kidney Injury, Appendicitis, Arrhythmias, Cardiac, Coronavirus, COVID-19, Herpes Zoster, Intracranial Hemorrhages, Lymphatic Diseases, Myocardial Infarction, Myocarditis, Pericarditis, Primary Prevention, Pulmonary Embolism, Risk Factors, RNA, Messenger, SARS-CoV-2, Thrombocytopenia, Thromboembolism, Vaccination, Vaccines, Venous Thrombosis
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