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Background: Recognising the importance of attaining high vaccine coverage to mitigate the COVID-19 impact, a Vaccine Pass scheme was implemented during and after the first large Omicron wave with high mortality in older ages in Hong Kong in early 2022 requiring three doses by June 2022. We did not identify any studies evaluating the policy impact of vaccination mandates with vaccine uptake over whole policy period of time in a Chinese population. We aim to evaluate the impact of the Vaccine Pass policy on COVID-19 vaccine uptake in adults in a Chinese population in Hong Kong., Methods: We analysed patterns in vaccine uptake and hesitancy using local data from population vaccine registry and 32 cross-sectional telephone surveys conducted from October 2021 to December 2022. The association of Vaccine Pass phases with vaccine uptake was examined using logistic regression analyses, taking into account covariates including self-risk perception, perceived self-efficacy in preventing COVID-19 and trust in government in pandemic control as well as physical distancing measures and demographics., Results: The uptake of primary series and third doses was positively significantly associated with the successive stages of Vaccine Pass implementation (adjusted odds ratios ranged from 2.41 to 7.81). Other statistically significant drivers of uptake included age group, chronic condition, higher perceived personal susceptibility to COVID-19, higher trust in government, and higher educational attainment., Conclusion: Vaccine uptake in older adults was observed to have increased by a greater extent after the policy annoucement and implementation, under the contextual changes during and after a large Omicron wave with high mortality in Hong Kong in early 2022. Since the policy withdrawal the uptake of further booster doses has been very low in all ages. We suggest that improving voluntary booster uptake in older adults should be prioritized., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Ben Cowling reports financial support was provided by Health Bureau. Ben Cowling reports financial support was provided by Research Grants Council. Ben Cowling reports a relationship with AstraZeneca that includes: consulting or advisory. Ben Cowling reports a relationship with Fosun Pharma that includes: consulting or advisory. Ben Cowling reports a relationship with GlaxoSmithKline that includes: consulting or advisory. Ben Cowling reports a relationship with Haleon that includes: consulting or advisory. Ben Cowling reports a relationship with Moderna that includes: consulting or advisory. Ben Cowling reports a relationship with Novavax that includes: consulting or advisory. Ben Cowling reports a relationship with Pfizer Inc that includes: consulting or advisory. Ben Cowling reports a relationship with Roche that includes: consulting or advisory. Ben Cowling reports a relationship with Sanofi Pasteur that includes: consulting or advisory. Ben Cowling reports a relationship with Fosun Pharma that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Conflict of 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., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

We studied 2780 adults in Hong Kong who received CoronaVac inactivated virus vaccine (Sinovac) and BNT162b2 mRNA vaccine ("Comirnaty", BioNTech/Fosun Pharma). We compared rates of antibody waning over time using an enzyme-linked immunosorbent assay for spike receptor binding domain and a surrogate virus neutralization test. We found stronger and more durable antibody responses to two doses of the mRNA vaccine, and slightly stronger initial antibody responses to each vaccine in younger adults and women. The weaker and less durable responses following CoronaVac support earlier provision of third doses to persons who previously received two doses of this vaccine., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: ‘Ben Cowling reports a relationship with Fosun Pharma USA Inc that includes: consulting or advisory. Ben Cowling reports a relationship with AstraZeneca that includes: consulting or advisory. Ben Cowling reports a relationship with GSK that includes: consulting or advisory. Ben Cowling reports a relationship with Moderna Therapeutics Inc that includes: consulting or advisory. Ben Cowling reports a relationship with Pfizer that includes: consulting or advisory. Ben Cowling reports a relationship with Roche that includes: consulting or advisory. Ben Cowling reports a relationship with Sanofi Pasteur that includes: consulting or advisory. BJC consults for AstraZeneca, Fosun Pharma, GSK, Moderna, Pfizer, Roche and Sanofi Pasteur. The authors report no other potential conflicts of interest.’., (Copyright © 2022 The Author(s). Published by Elsevier Ltd.. All rights reserved.)