U.S. study was conducted during Delta variant dominance

Two doses of the BNT162b2 vaccine proved to be 94% effective for preventing Covid-19 hospitalizations in teens and 98% effective for preventing Covid-related ICU admissions in a nationwide study involving adolescent patients conducted when the SARS-CoV-2 Delta variant was predominant in the United States.

The real-world effectiveness trial, conducted by the U.S. Centers for Disease Control and Prevention, compared vaccination status among 12- to 18-year-old patients hospitalized for Covid-19 (cases) to hospitalized adolescents who either were SARS-CoV-2 negative with symptoms consistent with Covid-19, or who did not have similar symptoms.

Just 4% of the 445 cases enrolled in the trial had received two doses of the BNT162b2 vaccine, while 36% of the 777 controls were fully vaccinated with the BNT162b2 vaccine, which is the only Covid-19 vaccine approved by the U.S. Food and Drug Administration for use in children and adolescents.

The study findings, published online Jan. 12 in New England Journal of Medicine, indicate that “nearly all hospitalizations and deaths in this population could have been prevented by vaccination,” wrote pediatric infectious disease specialist Kathryn Edwards, MD, of Vanderbilt University Medical Center, Nashville, who was not involved with the study.

In all, 40% of the patients hospitalized for Covid-19 required ICU admission and 29% required life support.

Just 2 of the 180 adolescents with Covid-19 who were admitted to the ICU had received two doses of vaccine, and none of the 7 teens who died had been fully vaccinated.

In an editorial, Edwards characterized the findings as “extremely encouraging,” while highlighting the missed opportunity to further reduce Covid-19 illness among vulnerable adolescents.

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

CDC epidemiologist and researcher Samantha Olson, MPH, and colleagues used a case-control, test-negative design to study real-world Covid-19 vaccination efficacy in adolescents against a range of outcomes, including hospitalization, admission to an ICU, need for life support (mechanical ventilation, vasopressors, and ECMO), and death.

Between early June and late October 2021, the researchers screened hospital admission logs for eligible cases with laboratory-confirmed Covid-19 at the 31 hospitals in 23 U.S. states participating in the Overcoming Covid-19 surveillance network.

A total of 445 cases and 777 controls were included in the analysis, and nearly three quarters of both the cases and controls had underlying medical conditions, including obesity. The median age of the case and control subjects was 16 years and 15 years, respectively, and 70% were attending on-site schools.

“We estimated vaccine effectiveness by comparing the odds of antecedent full vaccination (two doses of BNT162b2) in case patients as compared with two hospital-based control groups: patients who had Covid-19 like symptoms but negative results on testing for SARS-CoV-2 (test-negative) and patients who did not have Covid-19-like symptoms (syndrome-negative),” they wrote.

Among the Covid-19 cases, 4% were fully vaccinated, <1% were partially vaccinated, and 96% were unvaccinated, while 36% of controls were fully vaccinated, 7% were partially vaccinated, and 57% were unvaccinated.

The analysis also revealed that:

  • The overall effectiveness of the BNT162b2 vaccine against hospitalization for Covid-19 was 94% (95% CI, 90-96); with 95% effectiveness (95% CI, 91-97) among test-negative controls and 94% (95% CI, 89-96) among syndrome-negative controls.
  • The effectiveness was 98% against ICU admission and 98% against Covid-19 resulting in life support measures, and all seven deaths occurred in patients who were unvaccinated.
  • Underlying medical conditions, including obesity, were common among the hospitalized adolescents who were vaccinated (73%) and among those who were not (71%), but respiratory and endocrine disorders were more common in cases (33% and 16% respectively in cases and 23% and 11% respectively, in controls.

“In this real-world evaluation of the effectiveness of the BNT162b2 mRNA vaccine in adolescents between 12 and 18 years of age in the United States, when the Delta variant was predominant, we found that the vaccine was highly effective against Covid-19 hospitalization and critical illness, including among patients with underlying risk factors for severe illness,” Olson and co-authors wrote.

In her editorial, Edwards urged that the Overcoming Covid-19 surveillance network “continue to monitor hospitalization data over time to assess waning of immunity, protection against new variants of concern (particularly the rapidly spreading B.1.1.529 [omicron] variant), and the need for and timing of additional vaccine doses.”

  1. Two doses of the Pfizer-BioNTech mRNA vaccine proved to be 94% effective for preventing Covid-19 hospitalizations in teens and 98% effective for preventing Covid-related ICU admissions in a nationwide study.

  2. The data were collected when the SARS-CoV-2 Delta variant was predominant in the United States.

Salynn Boyles, Contributing Writer, BreakingMED™

This research was funded by the Centers for Disease Control and Prevention under a contract with Boston Children’s Hospital.

S. Olson and other researchers are employed by the CDC.

Cat ID: 125

Topic ID: 79,125,730,933,125,190,926,138,44,192,561,927,928,195,929