Short-term safety of COVID-19 vaccines in the underage population of Buenos Aires

Introduction: COVID-19 vaccines were developed in record time and only received emergency use authorization. There is still a limited data on the safety of paediatric vaccines for this disease. Objective: To determine the adverse events attributable to vaccination/immunization (ESAVI) associated with COVID-19 vaccines administered to individuals under 18 years of age. Methodology: An active pharmacovigilance process was carried out through a prospective, observational, and descriptive study on the short-term safety of paediatric SARS-CoV-2 vaccines. Children older than 6 months and younger than 18 years who had received at least one dose of a SARS-CoV-2 vaccine at Elina de la Serna Hospital in Montes de Oca between February and August 2023 were included. Data were collected via a WhatsApp survey conducted at 24 hours and 7 days post-vaccination. Variables considered included age, place of residence, recorded comorbidities, vaccine type and dose administered, and concomitant vaccinations. Data are presented as percentages, means, or rates, with corresponding confidence intervals. Results: A total of 545 children were included in the study, with a mean age of 9.6 years (95% CI: 5–13.8). Of the vaccines administered, 46.7% (n=129) were Moderna Pediatric, 32.6% (n=90) Pfizer Bivalent, 14.9% (n=41) Pfizer Pediatric, 4.7% (n=13) Beijing Institute, and 1.1% (n=3) Moderna Bivalent. At the time of vaccination, 12.1% (n=33) of patients had comorbidities. At 24 hours, 58.3% (n=161) of participants reported fever or injection site pain, and 25.4% (n=70) of them still had symptoms at 7 days. Only 2.2% (n=6) reported symptoms that required medical consultation. No hospitalizations or deaths were recorded. The relative risk (RR = 0.79) indicates that those vaccinated with Pfizer Bivalent had a 21% lower risk of presenting symptoms at 24 hours compared to those vaccinated with Moderna Pediatric. The symptoms can be considered mild, as only 4 patients required medical consultation. Conclusion: COVID-19 vaccination in children showed a low incidence of serious ESAVI in the short-term post-immunization period.