Association Between Influenza Vaccination Status and Confirmed Influenza Illness Among Healthcare Workers at Bamrasnaradura Infectious Diseases Institute: A Retrospective Case-Control Study
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Abstract
Influenza vaccination is a key preventive measure for healthcare workers (HCWs); however, influenza illness continues to occur in this population. This study aimed to identify factors associated with laboratory- confirmed influenza, with a particular focus on vaccination status, among HCWs at Bamrasnaradura Infectious Diseases Institute. A retrospective case-control study was conducted using data from January to December 2024. A total of 274 HCWs presenting with influenza-like illness (ILI) were included, comprising 44 laboratory-confirmed influenza cases and 230 test-negative controls. Data were analyzed using descriptive statistics and multiple logistic regression.
The results revealed that the majority of the case group were female (86.4%), with a mean age of 41.59 years. Approximately 63.6% of the cases had underlying diseases, and most of their working settings were classified as low-risk (40.9%). Furthermore, 65.9% of the cases had received the influenza vaccine within 12 months prior to their illness. Influenza A was the predominantly detected viral strain (79.5%). Multiple logistic regression analysis identified significant independent risk factors associated with influenza illness, which included being unvaccinated against influenza (adjusted odds ratio [aOR] = 2.13; 95% CI: 1.01-4.51, p = 0.047), having underlying diseases (aOR = 2.52; 95% CI: 1.15-5.51, p = 0.021), and working in moderate-risk settings (aOR = 24.39; 95% CI: 4.21-141.35, p < 0.001).
In conclusion, lack of influenza vaccination, underlying diseases, and moderate-risk occupational exposure were significantly associated with influenza illness among HCWs. These findings highlight the importance of strengthening annual influenza vaccination programs, particularly among high-risk groups, to reduce infection rates and enhance occupational safety.
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References
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