TY - JOUR
T1 - Post-COVID-19 multimorbidity incidence by prior vaccination status in people with a pre-existing comorbidity: A population-based cohort study
AU - Liu, Boyan
AU - Song, Song
AU - Liu, Wenlong
AU - Hu, Yuqi
AU - Wei, Cuiling
AU - Zhou, Lingyue
AU - Sun, Qi
AU - Tian, Wenxin
AU - Chu, Rachel Yui Ki
AU - Wong, Ian Chi Kei
AU - Hung, Ivan Fan Ngai
AU - Wan, Eric Yuk Fai
AU - Li, Xue
AU - Chui, Celine Sze Ling
AU - Chan, Esther Wai Yin
AU - Wong, Carlos King Ho
AU - Lai, Francisco Tsz Tsun
N1 - Copyright © 2025 The Author(s). Published by Elsevier Ltd on behalf of The British Infection Association. This is an open access article under the CC BY license (https://creativecommons.org/licenses/by/4.0/).
PY - 2025/9
Y1 - 2025/9
N2 - Background: Long-term health consequences of COVID-19, particularly among individuals with pre-existing chronic diseases, are not fully understood. This study investigates whether SARS-CoV-2 infection increases the risk of developing multimorbidity (≥2 chronic conditions) and evaluates protective effects of vaccination. Methods: We analyzed territory-wide electronic health records from Hong Kong, linking Hospital Authority data with COVID-19 infection and vaccination records from the Department of Health. A retrospective matched-cohort study was conducted among patients with one pre-existing chronic condition. Participants were stratified into three groups: (1) no documented COVID-19 infection, (2) COVID-19 infection with incomplete vaccination (<3 doses), and (3) COVID-19 infection with full vaccination (≥3 doses). The primary outcome was the incidence of a second chronic condition from a pre-specified list. Results: Among 1,038,175 eligible individuals, 68,975 (6.64%) developed multimorbidity over a median follow-up of 192 days (IQR: 96–313). The non-COVID-19 group (51,288 cases) had an incidence rate of 68.88 per 1000 person-years (95% CI: 68.18–69.37). In contrast, the COVID-19/unvaccinated group (9455 cases) exhibited a significantly higher rate (86.58; 95% CI: 84.85–88.35). The COVID-19/vaccinated group (8232 cases) showed a moderated rate (72.84; 95% CI: 71.27–74.43). Adjusted incidence rate ratios were 1.26 (95% CI: 1.23–1.29) for unvaccinated and 1.08 (95% CI: 1.05–1.11) for vaccinated individuals compared to the non-COVID-19 group. Results remained consistent across age, sex, and comorbidity subgroups. Interpretation: COVID-19 infection is associated with an increased risk of multimorbidity in patients with pre-existing conditions. Full vaccination attenuates this risk substantially, highlighting its critical role in mitigating post-infection complications.
AB - Background: Long-term health consequences of COVID-19, particularly among individuals with pre-existing chronic diseases, are not fully understood. This study investigates whether SARS-CoV-2 infection increases the risk of developing multimorbidity (≥2 chronic conditions) and evaluates protective effects of vaccination. Methods: We analyzed territory-wide electronic health records from Hong Kong, linking Hospital Authority data with COVID-19 infection and vaccination records from the Department of Health. A retrospective matched-cohort study was conducted among patients with one pre-existing chronic condition. Participants were stratified into three groups: (1) no documented COVID-19 infection, (2) COVID-19 infection with incomplete vaccination (<3 doses), and (3) COVID-19 infection with full vaccination (≥3 doses). The primary outcome was the incidence of a second chronic condition from a pre-specified list. Results: Among 1,038,175 eligible individuals, 68,975 (6.64%) developed multimorbidity over a median follow-up of 192 days (IQR: 96–313). The non-COVID-19 group (51,288 cases) had an incidence rate of 68.88 per 1000 person-years (95% CI: 68.18–69.37). In contrast, the COVID-19/unvaccinated group (9455 cases) exhibited a significantly higher rate (86.58; 95% CI: 84.85–88.35). The COVID-19/vaccinated group (8232 cases) showed a moderated rate (72.84; 95% CI: 71.27–74.43). Adjusted incidence rate ratios were 1.26 (95% CI: 1.23–1.29) for unvaccinated and 1.08 (95% CI: 1.05–1.11) for vaccinated individuals compared to the non-COVID-19 group. Results remained consistent across age, sex, and comorbidity subgroups. Interpretation: COVID-19 infection is associated with an increased risk of multimorbidity in patients with pre-existing conditions. Full vaccination attenuates this risk substantially, highlighting its critical role in mitigating post-infection complications.
KW - COVID-19
KW - Long-COVID
KW - Multimorbidity
KW - Primary health care
KW - Public health
KW - Vaccination
UR - https://www.journalofinfection.com/article/S0163-4453(25)00197-5/fulltext
UR - http://www.scopus.com/inward/record.url?scp=105013991673&partnerID=8YFLogxK
U2 - 10.1016/j.jinf.2025.106597
DO - 10.1016/j.jinf.2025.106597
M3 - Article
SN - 0163-4453
VL - 91
JO - Journal of Infection
JF - Journal of Infection
IS - 3
M1 - 106597
ER -