Clinical Trials – Vaccine Safety

Page last reviewed 21 April 2023

Key Points

Key Points are meant to be a scientific, factual summary of the available information that relates solely to the Pfizer-BioNTech COVID-19 Vaccine, as supported by referenced publications within this section. Conclusions should not be drawn from the inclusion or absence of information.

Pfizer-BioNTech Vaccine-related Safety Key Points References
Most Common Adverse Drug Reactions (ADRs)
  • The safety and reactogenicity of a primary series (2 doses) of monovalent BNT162b2 were evaluated in clinical trials in children, adolescents, and adults.
    • The most frequently reported ADRs were:


      Ages 5–11 years1 Ages 12–15 years2 Age ≥ 16 years3

      Pain at injection site:

      • 71–74%

      Pain at injection site:

      • 79–86%

      Pain at injection site:

      • 66–83%


      • 34–39%


      • 60–66%


      • 34–59%


      • 22–28%


      • 55–65%

      Muscle pain:

      • 14–37%

    • No cases of myocarditis or pericarditis were observed.1-6

    • Follow-up through 6 months post vaccination in age ≥ 16 years demonstrated a comparable safety profile to the pivotal study3,4
  • The safety and reactogenicity of a 3rd dose (1st booster) of BNT162b2 were evaluated in clinical trials in participants ≥ 16 years5, and these were consistent with findings of the previously listed clinical trials.1–6 Lymphadenopathy was observed at higher frequency in patients receiving a booster dose compared to 2 doses.3,5
  • Special populations:
    • A sub-analysis in participants with past or active neoplasms, ages ≥ 16 years showed similar safety profile as the overall trial population. The most common AEs in this population were pain at injection site, fatigue, and pyrexia.6
(1) Walter; (2) Frenck; (3) Polack; (4) Thomas NEJM 2021; (5) Moreira; (6) Thomas Vaccine 2022
ADRs identified during Post-marketing surveillance7,8
  • Cardiac: myo/pericarditis*
  • Gastrointestinal: diarrhea, vomiting
  • Immune: severe allergic reactions, including anaphylaxis; other hypersensitivity reactions (rash, pruritus, urticaria, angioedema)
  • Musculoskeletal and connective tissue: pain in extremity (arm)
  • Nervous system: syncope
(7) Prescribing Information for Pfizer-BioNTech COVID-19 Vaccine (2023-2024 Formula) for 12 Years of Age and Older;(8) Fact Sheet For Healthcare Providers Administering Vaccine: Emergency Use Authorization Of Pfizer-BioNTech Covid-19 Vaccine (2023-2024 Formula) for 6 Months Through 11 Years Of Age
General considerations
  • The safety profile of BNT162b2 was favorable in clinical trials in children, adolescents, and adults.1-6
  • Rates of serious ADRs and study withdrawal due to serious ADRs was extremely low (< 1%) and similar to placebo across studies.1-6
  • The most common ADRs were reported at slightly higher rates in ages 12–15 compared to 5–11 and ≥ 16 years.1-6
  • Participants > 55 years of age reported lower rates of pain at injection site, fatigue, and muscle pain when compared to ages 16–55.3
(1) Walter; (2) Frenck; (3) Polack; (4) Thomas NEJM 2021; (5) Moreira; (6) Thomas Vaccine 2022

*Data from multiple real-world evidence studies show a rare risk for myocarditis and/or pericarditis following receipt of mRNA COVID-19 vaccines. In clinical trials to support licensure, myocarditis and pericarditis were reported infrequently(1-6). Due to the cross-over design of clinical trials, the actual incidence of myocarditis cannot be reliably estimated. The low number of study cases preclude any firm or statistically powered conclusions regarding factors that could have contributed to the events. Please refer to the Real-World Evidence Vaccine-Associated Myo/pericarditis Key Point Summary for additional information on this topic.