COVID-19 vaccines for children have a strong safety record. Across clinical trials involving thousands of children and millions of real-world doses, most side effects have been mild and short-lived, with serious reactions remaining rare. Both the FDA and CDC continue to monitor pediatric vaccine safety through multiple surveillance systems, and the data consistently shows that the benefits of vaccination outweigh the risks for children aged 6 months and older.
What Clinical Trials Found
Before pediatric vaccines were authorized, they went through clinical trials specifically designed for children. The Pfizer vaccine was tested in 3,013 children aged 6 months through 4 years, while Moderna’s trial included 5,011 children aged 6 months through 5 years. In both trials, most adverse events were mild to moderate, and no serious vaccine-related adverse events were reported.
Children in these trials received lower doses than adults. For children 6 months through 11 years, the Moderna vaccine uses a 25-microgram dose, roughly a quarter of the adult dose. Pfizer’s version for children 5 through 11 uses 10 micrograms, one-third of the adult dose. These smaller doses were calibrated to produce a strong immune response while minimizing side effects.
Common Side Effects
The side effects children experience are similar to what adults report, just generally milder. The most common reactions include pain or swelling at the injection site, fever, tiredness, muscle or joint aches, headache, and swollen lymph nodes. Younger children (6 months through 3 years) may also cry more than usual, feel sleepy, or lose their appetite. Most children feel better within about three days.
Real-world data from the CDC’s v-safe monitoring system, where parents actively report how their child is doing after vaccination, confirms this pattern. Among children aged 5 through 11, about 55% of parents reported a local reaction like injection site pain after the first dose, and roughly 41% reported systemic reactions like fatigue or headache after the second dose. Around 5 to 7% of parents said their child couldn’t do normal daily activities the day after the shot, but this resolved quickly. Only about 1% of parents sought any medical care in the week after vaccination, and the vast majority of those visits were routine clinic appointments, not emergency situations.
Serious Side Effects Are Rare
Among the roughly 8.7 million doses given to children aged 5 through 11 during the initial rollout period, the CDC’s reporting system received 4,249 adverse event reports. Of those, 97.6% were classified as nonserious. Many of the “nonserious” reports weren’t even about side effects at all; the most common reports involved vaccine preparation or dosing issues, not reactions in the child.
For the youngest age group (6 months through 5 years), the pattern was similar. Out of 1,017 adverse event reports, 98.1% were nonserious. The most commonly reported issues were fever (about 20% of reports), rash (9.5%), vomiting (7.9%), and fatigue (6%). Nineteen reports were classified as serious, eight of which involved seizures. Among these, most children were not feverish at the time, and febrile seizures (seizures triggered by fever) are a known, typically harmless occurrence in young children with any vaccination or illness.
Myocarditis Risk in Context
Myocarditis, or inflammation of the heart muscle, has been the most closely watched potential side effect of mRNA vaccines. In the youngest children (6 months through 5 years), no cases of myocarditis were reported after vaccination during the initial monitoring period. Among children aged 5 through 11, 11 verified cases of myocarditis were identified out of 8.7 million doses. Of those 11 children, seven had fully recovered and four were recovering at the time of the report.
A large study published in The Lancet Child and Adolescent Health analyzed the health records of 13.9 million children and young people aged 5 through 18 in England. It found an estimated 0.85 extra cases of myocarditis or pericarditis per 100,000 vaccinated children. Importantly, COVID-19 infection itself also carries a risk of myocarditis, and unvaccinated children who get infected face heart-related complications at higher rates than vaccinated children do.
How Well the Vaccine Works
Safety matters most when weighed against benefit, and the vaccines provide meaningful protection. Data from the 2024-2025 season showed the updated vaccine was 76% effective at preventing COVID-related emergency department and urgent care visits in children aged 9 months through 4 years, and 56% effective in children and adolescents aged 5 through 17.
The vaccine also provides strong protection against one of the most dangerous COVID-related complications in children: Multisystem Inflammatory Syndrome in Children (MIS-C), a rare but serious condition where multiple organs become inflamed weeks after infection. Two doses of the vaccine were 91% effective at preventing MIS-C in adolescents aged 12 through 18. Among the 102 MIS-C patients studied, every single child who required life support was unvaccinated. No fully vaccinated child with MIS-C needed respiratory or cardiovascular life support, compared to 39% of unvaccinated MIS-C patients who did.
What’s Currently Available
The vaccine landscape for children has narrowed since the initial rollout. For the youngest children (6 months through 4 years), the only FDA-approved option is Moderna’s Spikevax. Pfizer’s vaccine is no longer authorized for this age group. Children aged 5 through 11 can receive either Moderna or Pfizer. The number of doses your child needs depends on their age and vaccination history, so checking the current CDC schedule for your child’s specific situation is worthwhile.
The CDC continues to track safety through two complementary systems. VAERS collects reports of any adverse events after vaccination, whether or not they’re caused by the vaccine. The v-safe program actively follows up with parents through surveys to capture how children are feeling in the days after each dose. Together, these systems provide an ongoing safety net that would detect any new concerns quickly. After hundreds of millions of pediatric doses administered worldwide, the safety profile of these vaccines in children remains reassuring.