Initial protection against Omicron in children and adolescents by BNT162b2

BACKGROUND The BNT162b2 (Pfizer-BioNTech) 2-dose vaccine for children and the BNT162b2 3rd dose for adolescents were approved shortly before the Omicron outbreak in Israel. The effects of these vaccines on the rates of Omicron confirmed infection are not yet clear. METHODS We extracted data for the Omicron-dominated (sub-lineage BA.1) period December 26, 2021 through January 8, 2022. We compared rates of confirmed Covid-19 infection between children 5-10 years old 14-35 days after receiving the 2nd dose to an internal control group of children 3-7 days after receiving the 1st dose (when the vaccine is not yet effective). Similarly, we compared confirmed infection rates in adolescents 12-15 years old 14-60 days after receiving a booster dose to an internal control group of adolescents 3-7 days after receiving the booster dose. We used Poisson regression, adjusting for age, sex, socioeconomic status, calendar week, and exposure. RESULTS In the 5-10 age group, the estimated rate of confirmed infection was 2.3 fold (95% CI, 2.0 to 2.5) lower in the 2nd dose group than in the internal control group. In adolescents, the third dose decreased confirmed infection rates by 3.3-fold (95% CI, 2.8 to 4.0). CONCLUSIONS A recent 2-dose BNT162b2 vaccination in children and a recent booster dose in adolescents reduced the rate of confirmed infection compared to the respective internal control groups. Future studies are needed to assess the duration of this protection and protection against other outcomes such as PIMS and long-COVID. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement No funding ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by the Institutional Review Board of the Sheba Medical Center. Helsinki approval number: SMC-8228-21. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes The individual-level data used in this study cannot be publicly shared even if anonymized due to privacy restrictions.