Slow Waning of Antibodies Following BNT162b2 as a Third Dose in Adults Who Had Previously Received 2 Doses of Inactivated Vaccine.

We administered BNT162b2 as a third dose to 314 adults aged ≥30 years who had previously received 2 doses of inactivated vaccine. We collected blood samples before the third dose and again after 1 month and 6 months, and found robust antibody responses to the ancestral strain at 6 months after receipt of BNT162b2. Antibody responses to Omicron BA.2 by live virus neutralization were weaker after the third dose and had declined to a low level by 6 months.

Competing Interests: Potential conflicts of interest. B. J. C. consults for AstraZeneca, Fosun Pharma, GlaxoSmithKline, Moderna, Pfizer, Roche, and Sanofi Pasteur, and has received research funding from Fosun Pharma. All other authors report no potential conflicts. All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.

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