Publication date: Dec 16, 2025
The benefit-risk of coronavirus disease 2019 (COVID-19) vaccination in children remains unclear. We evaluated the effects of mRNA vaccines on COVID-19 hospitalization, pericarditis/myocarditis, and MISC-C in children 6-17 years old. The Madrid Health System Registry was linked with 3 databases of the Madrilenian Health Service (primary care, hospital admissions, and pharmacy) to identify eligible children 6-17 years of age. We matched children receiving an mRNA vaccine with 5 controls and compared 240-day risks for vaccines and controls, with bootstrapping to obtain 95% confidence intervals. Effectiveness was defined as 1 minus the risk ratio. All analyses were conducted by age group (6-11 and 12-17 years). In 183,273 vaccinated and 916,365 controls 6-11 years old, the estimated risk difference (95% CI) of COVID-19 hospitalization was -1. 2 per 100,000 (-6. 6 to 4. 0) for vaccinated versus controls; effectiveness 9. 0% (-36 to 49). The risk difference of multisystem inflammatory syndrome in children was -1. 4 per 100,000 (-4. 7 to 2. 3); effectiveness 27. 0% (-54 to 76). No cases of myocarditis or pericarditis occurred. In 277,561 vaccinated and 1,387,805 controls 12-17 years old, the estimated risk difference of COVID-19 hospitalization was -5. 3 per 100,000 (-9. 0 to -2. 0); effectiveness 45% (18-72). The risk difference of multisystem inflammatory syndrome in children was -1. 3 per 100,000 (-3. 0 to 0. 8), effectiveness 42% (-31 to 83). The risk ratio of pericarditis/myocarditis for vaccinated versus controls was 1. 09 (0. 60-1. 70). The risks and benefits of COVID-19 vaccines were small in a general population of children 6-17 years of age.
| Concepts | Keywords |
|---|---|
| Coronavirus | observational study |
| Databases | target trial emulation |
| Hospitalization | vaccine effectiveness |
| vaccine safety |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | COVID-19 |
| disease | MESH | pericarditis |
| disease | MESH | myocarditis |
| disease | MESH | multisystem inflammatory syndrome in children |
| disease | MESH | Long Covid |