Moderna COVID-19 vaccine safe, effective in adolescents

The mRNA-1273 SARS-CoV-2 vaccine developed by Moderna demonstrates satisfactory safety profile in adolescents and produces an immune response comparable to that in young adults, according to the results of an interim analysis of an ongoing trial.

“The number of documented cases of COVID-19 is too small to generate robust assessments of vaccine efficacy,” the researchers said. “However, it appears that the mRNA-1273 vaccine safely induced levels of antiviral antibodies that should be protective against SARS-CoV-2 infection.”

In this ongoing phase II-III, placebo-controlled trial, 3,732 healthy adolescents (aged 12–17 years) were randomized 2:1 to receive two injections of the Moderna vaccine (100 μg in each; n=2,489) or placebo (n=1,243), administered 28 days apart.

The most common solicited adverse reactions among recipients of the Moderna vaccine after the first or second injections were injection-site pain (in 93.1 percent and 92.4 percent, respectively), headache (in 44.6 percent and 70.2 percent, respectively), and fatigue (in 47.9 percent and 67.8 percent, respectively). [N Engl J Med 2021;doi:10.1056/NEJMoa2109522]

The same reactions were noted among those in the placebo group after their first or second injections: injection-site pain (in 34.8 percent and 30.3 percent, respectively), headache (in 38.5 percent and 30.2 percent, respectively), and fatigue (in 36.6 percent and 28.9 percent, respectively). Serious adverse events related to mRNA-1273 or placebo did not occur.

Compared to young adults, the geometric mean titre ratio of pseudovirus neutralizing antibody titres in adolescents was 1.08 (95 percent confidence interval [CI], 0.94–1.24), and the absolute difference in serologic response was 0.2 percentage points (95 percent CI, –1.8 to 2.4), which met the criterion for noninferiority.

COVID-19 infection with an onset of 14 days after the second injection did not occur in the Moderna vaccine group, but four cases were reported in the placebo group. Of note, vaccine efficacy in this population was 93 percent, according to the less stringent case definition by the Centers for Disease Control and Prevention.

“The results from this trial involving adolescents extend the evidence of safety and efficacy of mRNA-1273 previously reported in adults,” the researchers said. [Vaccine 2021;39:2791-2799; N Engl J Med 2021;384:403-416]

“The primary immunogenicity objective was met and showed the noninferiority of immune response based on both the geometric mean titre and serologic response in adolescents as compared with that in young adults,” they added.

The exact role of adolescents in SARS-CoV-2 transmission remains unknown, but it is sound to assume that widespread vaccination in this age group could reduce community transmission and contribute to herd immunity. [JAMA Netw Open 2021;4:e218824-e218824; MMWR Morb Mortal Wkly Rep 2020;69:1925-1929; JAMA Pediatr 2021;175:143-156; Pediatrics 2021;147:e2020048090-e2020048090]

“Therefore, a safe and effective vaccine in adolescents could reduce COVID-19–related morbidity and mortality,” the researchers said. “The availability of effective vaccines in adolescents is also important to further reduce the reservoir of SARS-CoV-2.”

The BNT162b2 vaccine developed by Pfizer and BioNTech had been authorized for emergency use in adolescents aged 12–15 years. [N Engl J Med 2021;385:239-250; https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-pfizer-biontech-covid-19-vaccine-emergency-use]