Adverse events after COVID-19 vaccination in the pediatric population in Spain

INTRODUCTION: In December 2021, Spain launched its COVID-19 vaccination campaign for children aged 5-11 years. Although the Comirnaty® vaccine exhibited a favorable safety profile in premarketing trials, its rapid deployment and novel mRNA technology raised concerns among the public, leading to parental hesitancy. Real-world postmarketing data are limited but crucial for guiding clinical and public health policy decisions. OBJECTIVE: To assess the incidence and nature of adverse drug reactions (ADRs) following pediatric COVID-19 vaccination. METHODS: Prospective, observational and descriptive study cconducted at a tertiary care hospital in Spain. The sample consisted of a total of 2126 children aged 5-11 years. Data on ADRs were collected through telephone interviews, health record reviews and institutional registries. An expert committee evaluated each ADR using predefined criteria for causality and severity. RESULTS: Overall, 35.6% of participants reported at least one ADR, totaling 1437 reactions. Most were mild (99.5%) and resolved spontaneously. Only one case was classified as severe. The most common ADRs were injection site pain (57.1%), fever (11.1%) and headache (5.7%). There was no evidence of increased reactogenicity after the second dose. Of all ADRs, 65.1% were considered «definite» or «probable.» CONCLUSIONS: The Comirnaty® vaccine maintains a favorable safety profile in children under real-world conditions, with predominantly mild, self-limiting reactions and minimal need for medical care.