The mRNA-1273 vaccine is being developed to prevent COVID-19, the disease resulting from Severe Acute Respiratory Syndrome coronavirus (SARS-CoV-2) infection.
The study is designed to primarily evaluate the safety and reactogenicity of a single dose level of mRNA-1273 vaccine administered in 2 doses 28 days apart to an adolescent population.
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In this Phase 2/3 study, 3,732 adolescent participants ages 12 to less than 18 years were enrolled and randomized 2:1 to two 100 µg doses of mRNA-1273 or placebo.
The primary endpoint of non-inferior immunogenicity versus the Phase 3 adult study comparator group was met. After two doses, no cases of COVID-19 were observed in the vaccine group using the case definition from the adult Phase 3 COVE study, compared to 4 cases in the placebo group, resulting in a vaccine efficacy of 100% starting 14 days after the second dose.
Because the incidence rate of COVID-19 is lower in adolescents, a secondary case definition based on the CDC definition of COVID-19 was also evaluated to include cases presenting with milder symptoms.
Using the CDC definition, which requires only one COVID-19 symptom and a nasopharyngeal (NP) swab or saliva sample positive for SARS-CoV-2 by RT-PCR, a vaccine efficacy of 93% after the first dose was observed.
mRNA-1273 was generally well tolerated with a safety and tolerability profile generally consistent with the Phase 3 COVE study in adults. No significant safety concerns have been identified to date.
The majority of adverse events were mild or moderate in severity. The most common solicited local adverse event was injection site pain. The most common solicited systemic adverse events after the second dose of mRNA-1273 were headache, fatigue, myalgia, and chills.
On August 12, 2021, The New England Journal of Medicine published the results and conclusions of this clinical trial even though it is still active. The published conclusions are the mRNA-1273 vaccine had an acceptable safety profile in adolescents. The immune response was similar to that in young adults, and the vaccine was efficacious in preventing Covid-19. (Funded by Moderna and the Biomedical Advanced Research and Development Authority)