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Short-term adverse event profile of COVID-19 mRNA vaccines in Aussie kids: reassuring data from AusVaxSafety

A new research study published by AusVaxSafety, has shown that Australian children aged 5–15 years reported fewer side effects in the days following mRNA COVID-19 vaccination than in clinical trials.

Researchers analysed 396,920 survey responses captured via AusVaxSafety’s national active vaccine safety surveillance system following mRNA COVID-19 vaccine encounters in the first 15 months of use in children in Australia (i.e. between July 2021 and September 2022).  

In children aged 5–11 years, 25% of respondents – usually a parent or guardian of the child – reported at least one side effect in the first three days after Pfizer 10 micrograms dose 1 and 28% after Pfizer 10 micrograms dose 2. 

In children aged 12–15 years, 32% of respondents reported at least one side effect in the first three days after Pfizer 30 micrograms dose 1; 49% after Pfizer 30 micrograms dose 2; 34% after Moderna 100 micrograms dose 1; and 64% after Moderna 100 micrograms dose 2.

Local reactions (including pain, itching, redness and swelling at the injection site), fatigue, headache and muscle/joint pain were the most common side effects in both age groups. These side effects are known to occur after vaccination; they are generally mild and short-lived, with most resolving within one day or less. 

The rate of side effects reported was similar across sex and Indigenous status, but trended upwards with increasing age and was higher for children with parent-reported chronic medical conditions. Overall medical attendance rates remained low (0.7%) and overall impact on routine activities was also low (8.9%).

Importantly fever, which is a concern in children under 6 years of age due to the potential for febrile seizures, was low in the youngest age group and similar to that seen following annual influenza vaccination.

No self-reported cases of myocarditis or pericarditis were identified in this study and these data provide confidence to parents on the safety of mRNA COVID-19 vaccines used in Australia.

Few children received dose 3 of Pfizer 10 micrograms (for 5-11 years), any dose of Moderna 50 micrograms (for 6-11 years), or dose 3 of Moderna 100 micrograms (for 12-15 years) in Australia during the surveillance period. With fewer than 100 responses in each of the respective groups, they were excluded from this analysis. 

Access the published paper here
AusVaxSafety continue to monitor all brands and doses of COVID-19 vaccines currently in use in children and adolescents in Australia, with new safety data published on the AusVaxSafety website when sufficient data is received for analysis. 

Access the latest AusVaxSafety COVID-19 vaccine safety data here