Influenza vaccine protection and contact patterns among outpatients with influenza-like illness during the 2024-2025 season in China: a test-negative case-control study.
11 affiliations
- 1Institute of Medical Engineering Interdisciplinary Research, College of Medical Engineering and Technology, Xinjiang Medical University, Urumqi, Xinjiang, China.
- 2School of Public Health, Tianjin Medical University, Tianjin, China.
- 3Ili Kazakh Autonomous Prefecture Center for Disease Control and Prevention, Ili Kazakh Autonomous Prefecture, China.
- 4JC School of Public Health and Primary Care, The Chinese University of Hong Kong, Hong Kong, China.
- 5School of Public Health, The University of Hong Kong, Hong Kong, China.
- 6Department of Biomedical Sciences, City University of Hong Kong, Hong Kong, China.
- 7Health Commission of Ili Kazakh Autonomous Prefecture, Ili Kazakh Autonomous Prefecture, China.
- 8Department of Mathematics, The Hong Kong Polytechnic University, Hong Kong, China.
- 9Peking University Center for Public Health and Epidemic Preparedness & Response, MoE Key Laboratory of Epidemiology of Major Diseases, Department of Epidemiology and Biostatistics, School of Public Health, Peking University, Beijing, China.
- 10Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong, China.
- 11School of Public Health and Emergency Management, Southern University of Science and Technology, Shenzhen, China.
Abstract
Background
Continuous monitoring of both influenza vaccine protection and behavioural determinants of infection is important for understanding related risks. Evidence on influenza vaccine effectiveness (VE) in China during the 2024-2025 season, however, remains limited. We aimed to assess influenza VE among healthcare-seeking outpatients with influenza-like illness (ILI) and to examine the contact patterns associated with infection risk.Methods
We enrolled 928 outpatients with ILI from three sentinel hospitals in Ili Kazakh Autonomous Prefecture, China, between December 2024 and March 2025 in a test-negative case-control study. We confirmed influenza infection using reverse transcription-polymerase chain reaction and collected vaccination history and social contact frequency and duration through questionnaires. We estimated VE using logistic regression with covariate adjustment, and otherwise analysed social contact patterns and performed exploratory sequencing of six randomly selected influenza-positive samples.Results
Our full sample comprised 928 participants. We excluded 21 infants younger than 6 months from the VE analysis and included 907 participants, of whom 121 tested positive and 786 tested negative. The overall adjusted VE against medically attended influenza was 42.3% (95% credible interval = 11.1-62.5). In the analysis of social contacts for all 928 participants, test-positive children aged 0-10 years and adults aged 65 years or older reported more frequent and longer social contact than their test-negative counterparts. Exploratory sequencing of six samples suggested no major antigenic mismatch with the vaccine strains, but the very small number of sequenced samples limits the generalisability of this finding.Conclusions
Influenza vaccination provided moderate protection against medically attended influenza, while contact patterns were associated with infection risk among children and older adults. Combined vaccination and behavioural interventions warrant further evaluation, as the observational design of this study and its use of self-reporting data limit causal inference.
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BibTeX
@article{chen2026influenza,
title = {{Influenza vaccine protection and contact patterns among outpatients with influenza-like illness during the 2024-2025 season in China: a test-negative case-control study.}},
author = {Luping Chen and Jia Mi and Yingxuan Wang and Zhisheng Chen and Juping Wang and Zihao Guo and Haogao Gu and Qiaoge Chi and Lirong Cao and Ruijuan Ji and Kamuranni Luotebula and Shengmei Yang and Yan Kong and Kailu Wang and Sheikh Taslim Ali and Daihai He and Marc Kc Chong and Shi Zhao and Kai Wang and Yuantao Hao and David Sc Hui and Zijian Feng},
journal = {Journal of global health},
year = {2026},
month = oct,
doi = {10.7189/jogh.16.04253},
url = {https://europepmc.org/article/MED/42852605},
note = {CC BY},
}
RIS
TY - JOUR
TI - Influenza vaccine protection and contact patterns among outpatients with influenza-like illness during the 2024-2025 season in China: a test-negative case-control study.
AU - Luping Chen
AU - Jia Mi
AU - Yingxuan Wang
AU - Zhisheng Chen
AU - Juping Wang
AU - Zihao Guo
AU - Haogao Gu
AU - Qiaoge Chi
AU - Lirong Cao
AU - Ruijuan Ji
AU - Kamuranni Luotebula
AU - Shengmei Yang
AU - Yan Kong
AU - Kailu Wang
AU - Sheikh Taslim Ali
AU - Daihai He
AU - Marc Kc Chong
AU - Shi Zhao
AU - Kai Wang
AU - Yuantao Hao
AU - David Sc Hui
AU - Zijian Feng
PY - 2026
DA - 2026/10/09
JO - Journal of global health
DO - 10.7189/jogh.16.04253
UR - https://europepmc.org/article/MED/42852605
AB - Background Continuous monitoring of both influenza vaccine protection and behavioural determinants of infection is important for understanding related risks. Evidence on influenza vaccine effectiveness (VE) in China during the 2024-2025 season, however, remains limited. We aimed to assess influenza VE among healthcare-seeking outpatients with influenza-like illness (ILI) and to examine the contact patterns associated with infection risk.Methods We enrolled 928 outpatients with ILI from three sentinel hospitals in Ili Kazakh Autonomous Prefecture, China, between December 2024 and March 2025 in a test-negative case-control study. We confirmed influenza infection using reverse transcription-polymerase chain reaction and collected vaccination history and social contact frequency and duration through questionnaires. We estimated VE using logistic regression with covariate adjustment, and otherwise analysed social contact patterns and performed exploratory sequencing of six randomly selected influenza-positive samples.Results Our full sample comprised 928 participants. We excluded 21 infants younger than 6 months from the VE analysis and included 907 participants, of whom 121 tested positive and 786 tested negative. The overall adjusted VE against medically attended influenza was 42.3% (95% credible interval = 11.1-62.5). In the analysis of social contacts for all 928 participants, test-positive children aged 0-10 years and adults aged 65 years or older reported more frequent and longer social contact than their test-negative counterparts. Exploratory sequencing of six samples suggested no major antigenic mismatch with the vaccine strains, but the very small number of sequenced samples limits the generalisability of this finding.Conclusions Influenza vaccination provided moderate protection against medically attended influenza, while contact patterns were associated with infection risk among children and older adults. Combined vaccination and behavioural interventions warrant further evaluation, as the observational design of this study and its use of self-reporting data limit causal inference.
SN - 2047-2978
SN - 2047-2986
ER -