ORIGINAL RESEARCH article
Front. Public Health
Sec. Infectious Diseases: Epidemiology and Prevention
Volume 13 - 2025 | doi: 10.3389/fpubh.2025.1497399
Using surveillance data to evaluate the effectiveness of inactivated/ mRNA COVID-19 vaccine boosters in preventing the fatal outcome among severe COVID-19 cases in the current ambit of SARS-CoV-2 XBB and JN. 1 variants circulation
Provisionally accepted
Eugene SK Lo
Lok Tung Wong*
Serana CY SoKirran N MohammadKa Yi LawKam Suen ChanJason CL ChanDawin Lo
Kin Hang Kung
Shuk Kwan Chuang- Department of Health (Hong Kong), Hong Kong, Hong Kong, SAR China
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Background: Despite the rapid evolution of SARS-CoV-2 viruses, vaccines targeting ancestral strains remain widely used. This study evaluates the effectiveness of ancestral strain inactivated and mRNA COVID-19 vaccine boosters in preventing fatal outcomes among severe COVID-19 cases during the circulation of the XBB and JN.1 variants. Methods: We analyzed 2,157 severe COVID-19 cases (aged ≥50) reported to the Centre for Health Protection from the Hospital Authority-managed public hospitals between January 30, 2023, and January 29, 2024. Logistic regression was used to investigate the relationship between vaccination status and fatal outcomes, adjusting for age, sex, and residential status in residential care homes for the elderly (RCHE), and other demographic factors. Results: Among the 2,157 cases, 764 (35.4%) succumbed within a 28-day follow-up. Fatal outcomes were more common among older individuals, RCHE residents, and those unvaccinated or with incomplete initial vaccination (0-2 doses). Fewer deaths had received ancestral strain mRNA or inactivated booster doses compared to those not receiving booster. Univariate logistic regression revealed the lowest in-hospital mortality odds ratio for mRNA booster recipients, followed by inactivated booster recipients and then those with completed initial vaccination (3 doses). After adjusting for confounders, booster vaccination remained significantly associated with reduced in-hospital mortality. Conclusion: Vaccines based on ancestral strains maintain some degree of effectiveness against recently emerged variants offering insights for healthcare policies in regions where earlier generations of inactivated and mRNA vaccines continue to be administered.
Keywords: COVID- 19, Vaccine effectiveness, Vaccine, SARS- CoV- 2, Severe illness, Mortality, death, Booster dose
Received: 17 Sep 2024; Accepted: 21 Apr 2025.
Copyright: © 2025 Lo, Wong, So, Mohammad, Law, Chan, Chan, Lo, Kung and Chuang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Lok Tung Wong, Department of Health (Hong Kong), Hong Kong, Hong Kong, SAR China
Disclaimer: All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.