Adverse reactions in young children receiving the coronavirus disease 2019 vaccine

Background: We sought to investigate the occurrence of adverse reactions in Japanese children aged 6 months to 4 years who received the BNT162b2 coronavirus disease 2019 (COVID-19) vaccine, to examine parental considerations, and to evaluate potential risk factors associated with post-vaccination fever.
Methods: This cross-sectional survey study targeted 1617 children aged 6 months to 4 years who received their primary doses of BNT162b2 from November 10, 2022, to April 30, 2023, in Okayama Prefecture. We surveyed the occurrence of local and systemic reactions within 1 week after vaccination, and described the incidence proportions of adverse reactions for 515 participants overall and by age group. The study also examined the impact of previous COVID-19 infection and co-administration of the seasonal influenza vaccine on post-vaccination fever. A survey also assessed parents' reasons for vaccinating their children and the sources of information they used.
Results: Adverse reactions were infrequent (5.2%, with fever ≥37.5°C; no cases exceeded 39°C) and did not increase with vaccine doses administered. The risk of post-vaccination fever was not statistically associated with a history of COVID-19—the adjusted risk ratio (aRR) was 0.99, and the 95% confidence interval (CI) was 0.41–2.39—but was associated with co-administration of the seasonal influenza vaccine (aRR 3.24, 95% CI 1.14–9.18). Parental decisions regarding vaccination were influenced by official government guidelines and primary care physicians' opinion.
Conclusion: This study provides valuable insight into the safety profile of the BNT162b2 vaccine in Japanese children aged 6 months to 4 years. Further research involving larger cohorts and appropriate control groups is needed.

This is the peer reviewed version of the following article: [Matsumoto, N, Shimizu, J, Yokoyama, Y, Tsukahara, H, Yorifuji, T. Adverse reactions in young children receiving the coronavirus disease 2019 vaccine. Pediatr Int. 2023; 65:e15696. https://doi.org/10.1111/ped.15696], which has been published in final form at [https://doi.org/10.1111/ped.15696]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

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