Children who received a COVID-19 vaccine faced an increased risk of several adverse events, including swollen lymph nodes, researchers in Norway have found.
The Moderna and Pfizer-BioNTech vaccines in children aged 12 to 19 were linked to increased risks of severe allergic shock, lymphadenopathy, and heart inflammation. Increased risks of acute appendicitis, epilepsy, and convulsions were also detected.
The study population, which numbered almost 500,000, were born from 2002 to 2009 and received a COVID-19 vaccine in 2021 or 2022. They excluded children who received an early vaccine or who suffered one of the health problems under consideration within the four years prior to vaccination.
Researchers then analyzed data from the Norwegian Emergency Preparedness Register for COVID-19, which includes vaccinations and health care encounters, to see whether any of the 18 outcomes were associated with vaccination.
The main analysis applied a Poisson regression to estimate whether there was an increased risk of an outcome such as heart inflammation among the vaccinated, using unvaccinated children as a reference.
Researchers found children who received a COVID-19 vaccine were five times more likely to suffer an anaphylactic reaction, or severe allergic shock, after a first dose, and nearly 10 times more likely to suffer the shock after a second dose. The increased risks came within two days.
Vaccinated children were about 2.5 times more likely to suffer lymphadenopathy (swollen lymph nodes) within 14 days of a second dose and seven times more likely to suffer heart inflammation (myocarditis or pericarditis) within 28 days of a second dose, according to the results of the main analysis.
Phase three clinical trials detected an increased risk of swollen lymph nodes among participants aged 16 and up.
Researchers also found an increased risk of acute appendicitis following a first and second dose and an increased risk of facial nerve palsy. Risks of epilepsy and convulsions among 18- and 19-year-olds increased within 28 days, the risk window of a second vaccine dose.
There were additional increased risks outside the risk windows for some other health problems. Others were such rare problems to begin with that their failure to register statistically was hard to draw conclusions from.
“Although most outcomes studied were not significantly associated with vaccination, some (arrhythmia, arthropathy, cerebrovascular events, encephalomyelitis and meningitis, Guillain-Barré syndrome, Henoch-Schönlein purpura, idiopathic thrombocytopenic purpura and multisystem inflammatory syndrome in children cannot be ruled out due to rarity,” researchers explained.
“We found no statistically significant associations with all-cause mortality within 28 days. Events were very rare. No Norwegian adolescents were registered with vaccine-associated death,” the report stated.
The paper was published ahead of peer review on medRxiv. The authors said additional studies should be conducted to explore adverse events following child vaccination.
“Knowledge of potential post-vaccination adverse events is crucial to weigh benefits against risks, and for future vaccine recommendations,” wrote German Tapia, with the Norwegian Institute of Public Health and his co-authors.
“The number of observed outcomes and statistically significant associations were generally low in this study, with some exceptions which should be further monitored.”
Limitations included a possible healthy vaccinee effect, which refers to how people who get vaccines can be healthier than those who do not.
The authors listed no funding. However, several authors had done other work from some pharmaceutical companies, including Novo Nordisk and AstraZeneca.