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. 2024 Sep 5;12(9):1014.
doi: 10.3390/vaccines12091014.

Assessing the Impact of Primary-Series Infection and Booster Vaccination on Protection against Omicron in Hong Kong: A Population-Based Observational Study

Jialiang Jiang  1 , Eric Ho Yin Lau  2 , Ziyi Zhou  1 , Guosheng Yin  1 , Yun Lin  2 , Benjamin John Cowling  2   3 , Kwok Fai Lam  1   4
Affiliations

Assessing the Impact of Primary-Series Infection and Booster Vaccination on Protection against Omicron in Hong Kong: A Population-Based Observational Study

Jialiang Jiang et al. Vaccines (Basel). .

Abstract

This study aimed to assess the real-world effectiveness of vaccines and hybrid immunity in preventing infections during the Omicron prevalent period in Hong Kong. This study analyzed vaccination records and COVID-19 confirmed case records from 1 January 2022 to 28 January 2023 and included a total of 7,165,862 individuals with vaccination or infection records. This study found that an additional vaccine dose offered increased protection against Omicron BA.1/2 and BA.4 infections for individuals without prior infections in general. Hybrid immunity, acquired through vaccination and natural infection, was found to be significantly stronger than that provided by vaccines alone. The Comirnaty Original/Omicron BA.4/5 bivalent vaccine, introduced in December 2022, was associated with a lower risk of BA.4 infection when administered as a booster dose after three doses of CoronaVac. However, individuals with four doses of the CoronaVac vaccine did not exhibit a significantly lower risk of infection compared to those with three doses during the BA.4 dominant period. This study highlights the importance of promoting booster shot uptake and encouraging vaccination among those who have recovered from COVID-19 infections. The potential immune imprinting effect associated with the Comirnaty and CoronaVac vaccine underscores the need for continued surveillance and research to optimize vaccination strategies for emerging variants.

Keywords: Comirnaty; CoronaVac; Omicron; SARS-CoV-2.

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Conflict of interest statement

B.J.C. consults for AstraZeneca, Fosun Pharma, GlaxoSmithKline, Haleon, Moderna, Novavax, Pfizer, Roche, and Sanofi Pasteur. The authors declare no conflicts of interest.

Figures

Figure A1
Figure A1
(a) Daily number of infections for Comirnaty cohort in Scenario I; (b) daily number of infections for CoronaVac cohort in Scenario I.
Figure A2
Figure A2
(a) Daily number of infections for Comirnaty cohort in Scenario II; (b) daily number of infections for CoronaVac cohort in Scenario II.
Figure A3
Figure A3
(a) Daily number of infections for Comirnaty cohort in Scenario III; (b) daily number of infections for CoronaVac cohort in Scenario III.
Figure 1
Figure 1
The study period for Scenarios I, II, and III.
See this image and copyright information in PMC

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