Adverse Events Following the BNT162b2 mRNA COVID-19 Vaccine (Pfizer-BioNtech) in Aotearoa New Zealand

Lancet | 3 Feb 2023


Background:  In February 2021, New Zealand began its largest ever immunisation programme with the BNT162b2 mRNA COVID-19 vaccine. We aimed to understand the association between 12 adverse events of special interest (AESIs) and a primary dose of BNT162b2 in the New Zealand population, aged ≥ 5 years, from 19 February 2021 through 10 February 2022.

Methods: Using national electronic health records, the observed rates of AESIs within a risk period (0-21 days) following vaccination were compared to the expected rates based on background data (2014 – 2019). The incidence rate ratio (IRR) for each AESI was estimated with 95% confidence intervals (CI) and adjusted by age. The risk difference was calculated to estimate the excess number of events per 100,000 persons vaccinated.

Findings: As of 10 February 2022, 4,277,163 first and 4,114,364 second doses of BNT162b2 were administered to the eligible New Zealand population, aged ≥ 5 years. The observed rates of most AESIs post-vaccination were not statistically different than the expected rates. The IRR (95% CI) of myo/pericarditis following the first dose was 2.6 (2.2– 2.9) with a risk difference (95% CI) of 1.6 (1.1– 2.1) per 100,000 persons vaccinated and was 4.1 (3.7– 4.5) with a risk difference of 3.2 (2.6– 3.9) per 100,000 persons vaccinated following the second dose. The highest IRR was 25.8 (95% CI 15.6– 37.9) in the 5-19 years age group, following the second dose of the vaccine, with an estimated 5 additional myo/pericarditis cases per 100,000 persons vaccinated. An increased incidence of acute kidney injury (AKI) was observed following the first (1.6 (1.5– 1.6)) and second (1.7 (1.6– 1.7)) dose of BNT162b2.

Interpretation: Although rare, a statistically significant association between BNT162b2 vaccination and myo/pericarditis and AKI was observed. While the association between BNT162b2 and myo/pericarditis has been confirmed internationally, further research is required to understand the association of AKI. BNT162b2 was not found to be associated with most of the AESIs investigated, providing reassurances around the safety of the vaccine.

Funding: The work reported in this publication was undertaken during the COVID-19 Vaccine and Immunisation programme within the Ministry of Health New Zealand. Funding for this programme was provided by the New Zealand government. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Interest: The authors have no conflicts of interest to disclose.

Ethics Approval: The study did not require informed consent of individual participants as we used a deidentified dataset and received an exemption from New Zealand’s Health and Disability Ethics Committee (HDEC) of New Zealand (Reference #:2022 OOS 11950).

Keywords: COVID-19, mRNA Vaccines, BNT162b2, Adverse events, Pharmacoepidemiology

Suggested Citation:

Walton, Muireann and Pletzer, Vadim and Teunissen, Thomas and Lumley, Thomas and Hanlon, Timothy, Adverse Events Following the BNT162b2 mRNA COVID-19 Vaccine (Pfizer-BioNtech) in Aotearoa New Zealand. Available at SSRN: or

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