Real-world study confirms Pfizer vaccine's effectiveness among adolescents

A real-world study conducted at more than 30 U.S. hospitals demonstrated that the Pfizer-BioNTech vaccine was 94% effective at preventing hospitalization for COVID-19 among adolescents aged 12 to 18 years.

The study, which was conducted while delta was the predominant SARS-CoV-2 variant, also showed that the vaccine was 98% effective at preventing both ICU admission and need for life support. All seven deaths that occurred among the more than 1,200 adolescents enrolled in the study were in unvaccinated participants.

The study provided “impressive evidence” of the vaccine’s effectiveness in adolescents, Healio Pediatrics Editorial Board Member Kathryn M. Edwards, MD, wrote in an accompanying editorial.

“These extremely encouraging data indicate that nearly all hospitalizations and deaths in this population could have been prevented by vaccination,” Edwards, who is scientific director of the Vanderbilt Vaccine Research Program, wrote.

The researchers conducted a case-controlled, test-negative study that included 445 patients hospitalized with COVID-19 illness and 777 patients hospitalized with non-COVID illness. Only 17 case patients (4%) and 282 controls (36%) had been fully vaccinated.

Among the case patients, 180 (40%) were admitted to the ICU — only two were fully vaccinated — and 127 (29%) required life support, the researchers reported.

They calculated the overall effectiveness of the vaccine against hospitalization for COVID-19 to be 94% (95% CI, 90%-96%). Effectiveness was calculated as 95% (95% CI, 91%-97%) among test-negative controls and 94% (95% CI, 89%-96%) among syndrome-negative controls.

The researchers called for a “postauthorization monitoring of effectiveness” of vaccines “in order to understand vaccine performance in real-world settings.”

“Vaccine protection may differ in adolescents with underlying medical conditions, who are overrepresented in hospitalized settings and are often excluded from clinical trials,” they wrote. “Vaccine efficacy against new variants and according to the interval since vaccination could also vary.

In her editorial, Edwards said it was “distressing that less than 39% of the adolescents in the control group had been immunized against COVID-19, despite uniform eligibility and widespread vaccine access.”

“It is also highly problematic that three-quarters of the case patients had underlying conditions, that a disproportionate percentage were either Black (24%) or Hispanic (25%), and that nearly half the patients were enrolled in southern states, where immunization rates among adolescents have lagged,” Edwards wrote.

References:

Edwards KM. N Engl J Med. 2022;doi:10.1056/NEJMoa2118471.