A recent study published in the New England Journal of Medicine investigated the vaccine efficiency of the Pfizer BioNTech (BNT162b2) vaccine against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron variant in children and adolescents.
The increasing number of coronavirus disease 2019 (COVID-19)-related hospitalizations in the United States (US) has raised concerns regarding the efficiency of the vaccines and the immune evasion by SARS-CoV-2 variants.
Study: BNT162b2 Protection against the Omicron Variant in Children and Adolescents. Image Credit: Dkoi / Shutterstock
About the study
The present study assessed the duration of COVID-19 vaccine-induced protection among adolescents aged between 12 to 18 years during the periods when the SARS-CoV-2 Delta and Omicron variants were predominant. In addition, the team also studied the COVID-19-related hospitalizations observed among children and adolescents aged five to 18 years.
The team conducted a case-control, test-negative design study on participants hospitalized from 1 July 2021 to 18 December 2021 and 19 December 2021 to 17 February 2022, when the SARS-CoV-2 Delta and Omicron variants were predominant, respectively. The study included adolescents and children hospitalized due to COVID-19 in 31 pediatric hospitals in the US.
These patients were either hospitalized with COVID-19 being the primary cause of admission or with a clinical syndrome that was consistent with symptoms of acute COVID-19. Vaccination-related data of the patients were collected from the patient’s parents or guardians and included information on the dates of vaccination, the number of vaccine doses administered, whether the latest vaccine dose was received in the previous 14 days, the location of immunization, the vaccine manufacturer, and whether the patient had a COVID-19 vaccination card.
The case patients involved in this study had a positive reverse transcription-polymerase chain reaction (RT-PCR) result for SARS-CoV-2 or a positive antigen test result taken 10 days post symptom onset or within 72 hours of hospitalization. The study classified control patients as those hospitalized with a negative RT-PCR or antigen test result in the presence or absence of symptoms associated with COVID-19. The control patients were matched with a case patient who was hospitalized in the same institution as the control, belonged to the same age category, and was hospitalized within four weeks before or after the patient was hospitalized. The team assessed the duration of vaccine protection induced from two to 22 weeks and after 23 weeks in fully vaccinated adolescents aged 12 to 18 years.
The study results showed that out of the 3,234 patients eligible, 918 patients were categorized as case patients and 1,357 as control patients, all aged between 12 and 18 years. Also, a total of 684 and 234 case patients were hospitalized in the SARS-CoV-2 Delta and Omicron periods, respectively. The case and control patients were of a median age of 16 and 15 years while almost 78% and 67% of the patients had at least one comorbidity, respectively. Approximately 13% of the adolescent case patients were fully vaccinated, while 40% of the adolescent control patients were fully vaccinated.
Overall, 25% of the case patients had critical SARS-CoV-2 infection, including 14 patients who died. Among the case patients aged between 12 to 18 years, 27% of patients had critical SARS-CoV-2 infection, including 22 patients requiring extracorporeal membrane oxygenation and 13 patients who succumbed to COVID-19. Among the case patients aged five to 11 years, 16% suffered from critical COVID-19, including two patients who needed extracorporeal membrane oxygenation and one who died.
The study found similar vaccine effectiveness against the Delta and Omicron variants with 83% and 82% efficiency in case patients aged 12 to 15 years and 16 to 18 years, respectively. Moreover, vaccine effectiveness in preventing hospitalizations related to COVID-19 among adolescent case patients aged 12 to 18 years was 95% during the period of Delta predominance as compared to 40% during the Omicron period.
In the study cohort consisting of patients aged five to 11 years, vaccine effectiveness was found to be 68% against SARS-CoV-2-associated hospitalizations through the Omicron period. Notably, the time duration between the vaccine administration and COVID-19-related hospital admission during the Omicron period was 162 days among case patients aged 12 to 18 years as opposed to the 34 days interval in the patients aged five to 11 years.
The study findings showed that vaccination successfully reduced the risk of COVID-19-related hospitalization among children aged five to 11 years by two-thirds during the period of SARS-CoV-2 Omicron predominance. Also, the study noted that a majority of the children with critical SARS-CoV-2 infection were unvaccinated. Therefore, the researchers believe that continuous monitoring of vaccine efficacy against severe COVID-19 is crucial to forming robust vaccination strategies in the face of emerging SARS-CoV-2 variants.
- BNT162b2 Protection against the Omicron Variant in Children and Adolescents. A.M. Price, S.M. Olson, M.M. Newhams, N.B. Halasa, J.A. Boom, L.C. Sahni, P.S. Pannaraj, K. Irby, K.E. Bline, A.B. Maddux, R.A. Nofziger, M.A. Cameron, T.C. Walker, S.P. Schwartz, E.H. Mack, L. Smallcomb, J.E. Schuster, C.V. Hobbs, S. Kamidani, K.M. Tarquinio, T.T. Bradford, E.R. Levy, K. Chiotos, S.S. Bhumbra, N.Z. Cvijanovich, S.M. Heidemann, M.L. Cullimore, S.J. Gertz, B.M. Coates, M.A. Staat, M.S. Zinter, M. Kong, B.M. Chatani, J.R. Hume, K.V. Typpo, M. Maamari, H.R. Flori, M.W. Tenforde, L.D. Zambrano, A.P. Campbell, M.M. Patel, and A.G. Randolph. New England Journal of Medicine. 2022, DOI: 10.1056/NEJMoa2202826, https://www.nejm.org/doi/full/10.1056/NEJMoa2202826