Durability for 12 months of antibody response to a booster dose of monovalent BNT162b2 in adults who had initially received 2 doses of inactivated vaccine

We administered BNT162b2 as a third dose to 314 adults ≥30 years of age who had previously received 2 doses of inactivated vaccine. We collected blood samples before the third dose and again after 1, 6 and 12 months, and found stable levels of antibody responses to the ancestral strain and Omicron BA.2 at 6-12 months after receipt of the BNT162b2 third dose, with increased antibody levels in individuals who also received a fourth vaccine dose or reported a SARS-CoV-2 infection during follow-up. ### Competing Interest Statement B. J. C. consults for AstraZeneca, Fosun Pharma, GlaxoSmithKline, Haleon, Moderna, Novavax, Pfizer, Roche, and Sanofi Pasteur, and has received research funding from Fosun Pharma. All other authors report no potential conflicts. ### Clinical Trial The study is registered at [ClinicalTrials.gov][1] ([NCT05057182][2]). ### Funding Statement This project was supported by the Theme-Based Research Scheme T11-705/21-N of the Research Grants Council of the Hong Kong Special Administrative Region, China (to B. J. C.). B. J. C. is supported by a RGC Senior Research Fellow Scheme grant (HKU SRFS2021-7S03) from the Research Grants Council of the Hong Kong Special Administrative Region, China. ### 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 University of Hong Kong. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the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, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors [1]: https://ClinicalTrials.gov [2]: /lookup/external-ref?link_type=CLINTRIALGOV&access_num=NCT05057182&atom=%2Fmedrxiv%2Fearly%2F2023%2F08%2F21%2F2023.08.18.23294185.atom