The results of a large phase iii trial testing Moderna’s COVID-19 vaccine in children aged 12 to 17 have reportedly been published in the New England Journal of Medicine. The study showed that the vaccine was as safe and effective in adolescents. The trial followed nearly 4,000 young subjects between the ages of 12 and 17. These subjects received the same vaccine regimen and dose as previously tested and approved in adults.
As in previous trials, the most common side effects were injection site discomfort, headache and fatigue. No serious adverse events were seen in the trial, and the incidence of mild side effects was similar across all age groups.
Researchers have previously noted mild cardiac inflammation as a potentially rare side effect of the mRNA COVID-19 vaccine, which occurs mainly in young men. This trial did not find any cases of myocarditis or pericarditis, but it was also noted that these events were estimated to occur in about 13 cases per million doses and were therefore too rare to expect in this trial.
Serological tests showed that the immune response in the young subjects was similar to that seen in adults. Because of the low incidence of COVID-19 among adolescents, the trial lowers the criteria for defining a positive case, the researchers said. Only one symptom was used to classify symptomatic infection. Based on this lowered standard, the trial found no symptomatic cases after two doses of the vaccine, suggesting that the vaccine is highly effective in adolescents.
The researchers were careful to note that “the number of documented COVID-19 cases is too small to make a robust assessment of vaccine efficacy, however, it appears that the mrN-1273 vaccine safely induced levels of antiviral antibodies that should be protective against SARS-CoV-2 infection.”
Moderna first published the trial data in May, before it was peer-reviewed and published. At the time, Moderna said it would submit the data to regulators around the world.
In late July, the European Medicines Agency (EMA) approved Moderna’s vaccine for use in 12 – to 17-year-olds. However, the U.S. Food and Drug Administration (FDA) has not yet issued an emergency authorization for the vaccine’s use in adolescents, although Pfizer’s similar mRNA vaccine was approved for this age group in April.
Both Pfizer and Moderna are currently testing their mRNA vaccines in the under-12 age group. Citing concerns about rare side effects, the FDA recently asked the companies to expand these trials to include more children.
The ongoing trials are divided into three age groups: five to 11 years old, two to five years old, and six months to two years old. Pfizer’s trial is slightly more advanced than Moderna’s, and preliminary data for the 5 – to 11-year-old age group is expected as early as September.