Pfizer/BioNTech’s COVID-19 vaccine (Comirnaty) protected adolescents from severe COVID-19 outcomes, with high effectiveness against hospitalization, ICU admission, and need for life support, a case-control study found.

Vaccine effectiveness against hospitalization among adolescents ages 12-18 was 94% (95% CI 90-96), and 98% against both ICU admission and the need for life support, reported Manisha Patel, MD, of the CDC, and colleagues, on behalf of the Overcoming COVID-19 Investigators.

Of the 445 adolescents hospitalized for COVID, only 17 (4%) were fully vaccinated, the authors wrote in the New England Journal of Medicine.

In fact, there were only two fully vaccinated patients in the ICU and all seven deaths were among unvaccinated adolescents, the researchers noted.

“Vaccination averted nearly all life-threatening COVID-19 illness in this age group,” the team concluded.

Patel’s group cited the incidence of pediatric hospitalizations due to the Delta variant in early September 2021 as “an opportunity to evaluate the real-world effectiveness” of the Pfizer vaccine against severe COVID among adolescents and young teens.

This case-control, test-negative study examined data from July 1 to Oct. 25, 2021 among adolescents ages 12-18 at 31 hospitals in 23 states. Case patients were either hospitalized with COVID or had clinical symptoms consistent with COVID, and tested positive for SARS-CoV-2 via RT-PCR or antigen testing. Two groups were included as controls: those with COVID-like symptoms who tested negative and those without COVID-like symptoms who may or may not have been tested for SARS-CoV-2.

Vaccination status was based on either documentation or “plausible self-report,” and adolescents were considered to be fully vaccinated if they completed their two-dose vaccination series at least 14 days before illness onset.

Overall, there were 445 case patients and 777 controls. Median age was 15-16, 70-74% had underlying medical conditions, and 70% attended “in-person school.” Interestingly, 36% of controls were fully vaccinated.

While 71-73% of vaccinated and unvaccinated patients had obesity, case patients were more likely to have respiratory and endocrine disorders, while controls were more likely to have immunosuppressive or autoimmune disorders. Median length of hospital stay was 5 days among unvaccinated case patients and 4 days among vaccinated case patients.

Of the COVID-19 case patients, 40% (178 of the 180 patients unvaccinated) were admitted to the ICU and 29% (126 of 127 unvaccinated) received life support, including 3% who received extracorporeal membrane oxygenation and 2% who died. Among the fully vaccinated case patients admitted to the ICU, one had an immunosuppressive disorder, Patel’s group noted.

An accompanying editorial by Kathryn Edwards, MD, of Vanderbilt University Medical Center in Nashville, Tennessee, characterized the study as “impressive evidence regarding the effect of the vaccine in hospitalized adolescents.”

However, she called the low number of fully vaccinated adolescents in the control group “distressing … despite uniform eligibility and widespread vaccine access.” Edwards also pointed out that a “disproportionate percentage” of case patients were either Black (24%) or Hispanic (25%) and nearly half were from southern states.

“Although these rates have increased somewhat since the data in this study were compiled, as of December 1, 2021, only 60% of U.S. adolescents had received a single dose of a COVID-19 vaccine, and only 50% had been fully vaccinated,” she wrote.

Patel’s group noted limitations to the data, including the lack of effectiveness data against specific variants, potential lack of generalizability to patients with less severe disease presenting at non-urban hospitals, and that 56% of case patients were from southern states, which had higher COVID transmission.

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    Molly Walker is deputy managing editor and covers infectious diseases for MedPage Today. She is a 2020 J2 Achievement Award winner for her COVID-19 coverage. Follow

Disclosures

The views in this study are those of the authors and do not necessarily represent those of the CDC, the manuscript noted.

Patel noted no conflicts of interest; co-authors disclosed support from the CDC, NIH Clinical Center, AeorgenPharma, Abbott Laboratories, Sanofi Pasteur, BioFire Diagnostics LLC, Dynamed, Janssen Pharmaceuticals, Moderna, Pfizer, the National Institute of Allergy and Infectious Diseases, NIH, AstraZeneca, Seqirus, and Merck.

Edwards disclosed support from Elsevier, the Infectious Diseases Society of America, Moderna, Pfizer, PPD Development, and Sanofi Services, Inc.

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