Pfizer’s COVID-19 vaccine (Comirnaty) was 93% effective among adolescents at preventing hospitalization, even during the Delta surge, researchers found.
Among 179 patients ages 12-18 with COVID-19, 173 were unvaccinated, including 77 patients admitted to the ICU, 29 patients who were critically ill, and two that died, reported Samantha Olson, MPH, of the CDC, and colleagues, writing in an early edition of the Morbidity and Mortality Weekly Report.
Pfizer’s COVID-19 vaccine was highly effective among adolescents ages 12-15, showing 100% efficacy against symptomatic disease, which helped spur an amendment to the FDA emergency use authorization (EUA) in May. However, the authors noted that vaccine effectiveness data in real-world settings is “limited,” especially with regards to hospitalization in this population.
The researchers examined data from June 1 to September 30 across 16 states, from after the EUA was amended for vaccine use in adolescents ages 12-15 to when hospitalizations from Delta were highest.
This case-control study defined cases as adolescents hospitalized at one of 19 pediatric hospitals with symptomatic COVID-19-like illness and a positive test for SARS-CoV-2 via RT-PCR. Controls were patients with comparable symptoms, but who tested negative for SARS-CoV-2 and patients without COVID-19 who may or may not have received SARS-CoV-2 testing.
COVID-19 vaccination was defined as individuals who received two doses of Pfizer vaccine at least 14 days prior. Partially vaccinated individuals were excluded.
Overall, 464 patients, including 179 case patients and 285 controls, were included. Median age was 15, 72% had at least one underlying condition, and 68% attended in-person school, the authors noted. More case patients had diabetes versus controls (12% vs 5%), but more control patients had neurologic or neuromuscular disorders than case patients (28% vs 12%).
Among 169 case patients with available discharge data, median length of hospital stay was 5 days for unvaccinated patients compared with 3 days for vaccinated patients.
Vaccine effectiveness (VE) was 93% (95% CI 83%-97%) during the time period when Delta was dominant, the authors said. Notably, VE was similar among the 106 case patients ages 12-15 (91%) as among the 73 case patients ages 16-18 (94%).
The authors added that as of this report, only 46% of adolescents ages 12-15 and 54% of adolescents ages 16-17 are fully vaccinated against COVID-19.
“These data suggest that increasing vaccination coverage among this group could reduce the incidence of severe COVID-19 in the United States,” the team wrote.