ABSTRACT
AusVaxSafety (the Australian active safety surveillance system) used SMS/email delivered surveys to actively solicit the short-term (within first 3 days after vaccination) adverse event profile of mRNA COVID-19 vaccines in children (aged 5-15 years) by age, dose, brand and pre-existing comorbidity. 392,268 survey responses for children aged 5-15 who received a COVID-19 vaccine between July 2021 and May 2022 (211,994 following BNT162b2 10mcg in children aged 5-11 years, 173,329 following BNT162b2 30mcg and 6,945 following mRNA-1273 100mcg in adolescents aged 12-15 years) were analysed. Adverse event rates were higher following dose 2 and 3 compared to dose 1 after all vaccines and highest following dose 2 of mRNA-1273 in 12-15 years. Fever was low in the youngest children (5 years old, any dose; 1,090/26,181 (4%)). Medical review rates remained low (0.3% overall) and impact on daily activities was also low (7% overall). No self-reported cases of myocarditis or pericarditis were identified. Ongoing active safety surveillance of lower dose mRNA vaccines in children under 5 years old is required to better understand safety as the vaccines roll out into this population age-group.