Novavax’s COVID-19 Vaccine Demonstrates Efficacious, Safe Response in Adolescents


Analysis shows that the ratio of neutralizing antibody geometric mean titers in adolescents compared with young adults was 1.5 after vaccination with NVX-CoV2373.

Results from a clinical trial demonstrated that NVX-CoV2373 (Novavax), a COVID-19 vaccine, is efficacious, immunogenic, and safe in preventing the virus, including the predominant Delta variant, in adolescents.

Healthcare cure concept with a hand in blue medical gloves holding Coronavirus, Covid 19 virus, vaccine vial | Image Credit: Leigh Prather -

Leigh Prather -

Because of the efficacy and safety of the vaccine in adults, investigators expanded the PREVENT-19 trial (NCT04611802) to include adolescents aged 12 to 17 years. The expansion is a multicenter, phase 3, placebo-controlled, randomized, clinical trial in the United States.

Participants in the study were enrolled between April 26, 2021, and June 5, 2021, with the study still being conducted. A blinded crossover was implemented after 2 months of safety follow-up to include the active vaccine to all individuals in the study.

Investigators included known previous laboratory-confirmed COVID-19 infection or known immunosuppression as exclusion criteria.

The serologic inferiority of the neutralizing antibody responses compared with those of individuals aged 18 to 25 years in the PREVENT-19 trial were used as the main outcome, along with protective efficacy against laboratory-confirmed COVID-19, and the assessment of reactogenicity and safety.

Among the 2232 individuals, the mean age was 13.8 years, 52.5% were male, and 74.4% were white. Approximately 16.1% had a previous COVID-19 infection at baseline.

Investigators found that the ratio of neutralizing antibody geometric mean titers in adolescents compared with young adults was 1.5 after vaccination. There were 20 mild cases of COVID-19 after a median of 64 days of follow-up, which included 6 among those who received the vaccine. This indicates that the vaccine efficacy was approximately 79.5%.

Additionally, investigators found that the vaccine efficacy for the Delta variant was approximately 82%.

The reactogenicity was mild to moderate and transient, with a greater frequency after the second dose of the vaccine. Adverse events (AEs) were also more frequent in the vaccine recipient group compared with the placebo group.

The most reported local AEs were injection site pain and tenderness. The median duration for these events was approximately 2 days or less. The most common systemic AEs were fatigue, headaches, malaise, and myalgia. These AEs were also more commonly reported for vaccine recipients and after the second dose, with a median duration of 2 days or less.

Just 16.9% of individuals reported a fever of any severity after the second dose.

Serious AEs were rare and generally balanced between the treatments, with no AEs leading to discontinuation from the study. The serious systemic AEs included fatigue at 3.7% in the vaccine group and 3.4% in the placebo group after the first dose and 22% and 3.4% after the second.

Investigators found similar reactogenicity rates in age subgroups aged 13 to 14 years and aged 15 to 17 years.

There were several study limitations, including its short time period and when the vaccine efficacy of the primary series of 2 doses in 21 days was evaluated. The protective efficacy was also performed during the predominant circulation of the Delta variant, which was replaced by the Omicron variant. A booster dose given 5 to 6 months after the primary series is being assessed for all individuals included in the PREVENT-19 trial.


Áñez G, Dunkle LM, Gay CL, Kotloff KL, et al. Safety, immunogenicity, and efficacy of the NVX-CoV2373 COVID-19 vaccine in adolescents: a randomized clinical trial. JAMA Netw Open. 2023;6(4):e239135. doi:10.1001/jamanetworkopen.2023.9135

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