CLINICAL STUDIES — Expansion of the EUA was based on the results of a study (summarized in the FDA Fact Sheet) comparing the immunogenicity of two Novavax vaccine doses given 3 weeks apart in 390 adolescents 12-17 years old with that in 415 adults 18-25 years old. At 14 days after the second dose, the geometric mean anti-SARS-CoV-2 neutralizing antibody titer level was higher in the adolescent group than among the young adults (3859.6 vs 2611.8; geometric mean ratio 1.47 [95% CI 1.26-1.72]), and 99% of adolescents had experienced a seroresponse.3

In an observer-blind trial (PREVENT-19 expansion; summarized in the FDA Fact Sheet), 2247 adolescents 12-17 years old were randomized 2:1 to receive the Novavax vaccine or placebo at 0 and 3 weeks. Immunocompromised persons and those with a history of SARS-CoV-2 infection were excluded. In a descriptive per-protocol efficacy analysis in 1799 adolescents, PCR-confirmed COVID-19 with onset ≥7 days after the second dose was found to have occurred in 5 subjects who received the vaccine and in 11 who received placebo; the vaccine efficacy rate was 78.3% (95% CI 37.6%-92.5%). All COVID-19 cases in both groups were mild in severity, and all genetically sequenced cases were caused by the Delta variant of SARS-CoV-2.3

ADVERSE EFFECTS — Adverse effects of the Novavax vaccine in adolescents appear to be similar to those in adults. In the PREVENT-19 expansion, the most common severe adverse effects after the second vaccine dose were injection-site pain/tenderness (7.7%) and systemic myalgia (7.5%). Myocarditis occurred in one adolescent who received the vaccine.3

DOSAGE AND ADMINISTRATION — The FDA-approved dosage of the Novavax vaccine for primary immunization in adolescents is 0.5 mL (5 mcg of vaccine with 50 mcg of adjuvant) injected intramuscularly at 0 and 3 weeks, the same as that in adults.3 According to the CDC, an 8-week interval between doses may be optimal for immunocompetent adolescents, especially males, to reduce the small risk of myocarditis/pericarditis.4