• Hiam Chemaitelly, Sawsan AlMukdad, Houssein H Ayoub, Heba N Altarawneh, Peter Coyle, Patrick Tang, Hadi M Yassine, Hebah A Al-Khatib, Maria K Smatti, Mohammad R Hasan, Zaina Al-Kanaani, Einas Al-Kuwari, Andrew Jeremijenko, Anvar H Kaleeckal, Ali N Latif, Riyazuddin M Shaik, Hanan F Abdul-Rahim, Gheyath K Nasrallah, Mohamed G Al-Kuwari, Hamad E Al-Romaihi, Adeel A Butt, Mohamed H Al-Thani, Abdullatif Al-Khal, Roberto Bertollini, and Laith J Abu-Raddad.
• From the Infectious Disease Epidemiology Group (H.C., S.A., H.N.A., L.J.A.-R.) and the World Health Organization Collaborating Center for Disease Epidemiology Analytics on HIV/AIDS, Sexually Transmitted Infections, and Viral Hepatitis (H.C., S.A., H.N.A., L.J.A.-R.), Weill Cornell Medicine-Qatar, Cornell University, Qatar Foundation-Education City, the Mathematics Program, Department of Mathematics, Statistics, and Physics, College of Arts and Sciences, Qatar University (H.H.A.), and the Biomedical Research Center (P.C., H.M.Y., H.A.A.-K., M.K.S., G.K.N.) and the Departments of Biomedical Science (H.M.Y., H.A.A.-K., M.K.S., G.K.N.) and Public Health (H.F.A.-R., L.J.A.-R.), College of Health Sciences, QU Health, Qatar University, Hamad Medical Corporation (P.C., Z.A.-K., E.A.-K., A.J., A.H.K., A.N.L., R.M.S., A.A.B., A.A.-K.), the Department of Pathology, Sidra Medicine (P.T., M.R.H.), Primary Health Care Corporation (M.G.A.-K.), and the Ministry of Public Health (H.E.A.-R., M.H.A.-T., R.B.) - all in Doha, Qatar; the Departments of Population Health Sciences (H.C., H.N.A., A.A.B., L.J.A.-R.) and Medicine (A.A.B.), Weill Cornell Medicine, Cornell University, New York; and the Wellcome-Wolfson Institute for Experimental Medicine, Queen's University, Belfast, United Kingdom (P.C.).
• N. Engl. J. Med. 2022 Nov 17; 387 (20): 186518761865-1876.

BackgroundThe BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) has been authorized for use in children 5 to 11 years of age and adolescents 12 to 17 years of age but in different antigen doses.MethodsWe assessed the real-world effectiveness of the BNT162b2 vaccine against infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) among children and adolescents in Qatar. To compare the incidence of SARS-CoV-2 infection in the national cohort of vaccinated participants with the incidence in the national cohort of unvaccinated participants, we conducted three matched, retrospective, target-trial, cohort studies - one assessing data obtained from children 5 to 11 years of age after the B.1.1.529 (omicron) variant became prevalent and two assessing data from adolescents 12 to 17 years of age before the emergence of the omicron variant (pre-omicron study) and after the omicron variant became prevalent. Associations were estimated with the use of Cox proportional-hazards regression models.ResultsAmong children, the overall effectiveness of the 10-μg primary vaccine series against infection with the omicron variant was 25.7% (95% confidence interval [CI], 10.0 to 38.6). Effectiveness was highest (49.6%; 95% CI, 28.5 to 64.5) right after receipt of the second dose but waned rapidly thereafter and was negligible after 3 months. Effectiveness was 46.3% (95% CI, 21.5 to 63.3) among children 5 to 7 years of age and 16.6% (95% CI, -4.2 to 33.2) among those 8 to 11 years of age. Among adolescents, the overall effectiveness of the 30-μg primary vaccine series against infection with the omicron variant was 30.6% (95% CI, 26.9 to 34.1), but many adolescents had been vaccinated months earlier. Effectiveness waned over time since receipt of the second dose. Effectiveness was 35.6% (95% CI, 31.2 to 39.6) among adolescents 12 to 14 years of age and 20.9% (95% CI, 13.8 to 27.4) among those 15 to 17 years of age. In the pre-omicron study, the overall effectiveness of the 30-μg primary vaccine series against SARS-CoV-2 infection among adolescents was 87.6% (95% CI, 84.0 to 90.4) and waned relatively slowly after receipt of the second dose.ConclusionsVaccination in children was associated with modest, rapidly waning protection against omicron infection. Vaccination in adolescents was associated with stronger, more durable protection, perhaps because of the larger antigen dose. (Funded by Weill Cornell Medicine-Qatar and others.).Copyright © 2022 Massachusetts Medical Society.

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