Influenza Vaccination Status and Clinical Outcomes Among Adults Hospitalized with Community-Acquired Pneumonia: A Retrospective Cohort from Saudi Arabia.

BACKGROUND

Influenza vaccination is widely recommended to prevent influenza and its complications; however, its association with clinical outcomes among high-risk populations remains uncertain. This study aimed to investigate the association between influenza vaccination status and clinical outcomes among adults hospitalized with community-acquired pneumonia (CAP) in Saudi Arabia.

METHODS

This retrospective cohort study included adults hospitalized with CAP in Saudi public hospitals between October 2023 and March 2024. Data on demographic characteristics, comorbidities, influenza vaccination status, laboratory-confirmed influenza infection, intensive care unit (ICU) admission, in-hospital mortality, and length of hospital stay were obtained from electronic health records. Logistic regression analyses were performed to evaluate the associations between influenza vaccination and clinical outcomes.

RESULTS

Among 485 patients, 114 (23.5%) had received the seasonal influenza vaccine. The prevalence of laboratory-confirmed influenza infection was similar among vaccinated and unvaccinated patients (57.9% vs. 58.5%, p-value = 0.910). Vaccinated patients were less likely to require ICU admission (1.8% vs. 7.5%, p-value = 0.025), while no significant differences were observed in length of hospital stay or in-hospital mortality. After adjustment for age, sex, and comorbidities, influenza vaccination was associated with lower odds of ICU admission (OR = 0.200, 95% CI: 0.045, 0.894). No significant associations were observed between influenza vaccination and laboratory-confirmed influenza infection, length of hospital stay, or in-hospital mortality.

CONCLUSIONS

Among adults hospitalized with CAP in Saudi Arabia, influenza vaccination was associated with a lower likelihood of ICU admission, supporting its potential role in reducing disease severity among high-risk populations.