Reducing major cause-specific hospitalization rates and shortening hospital stays after influenza vaccination.

BACKGROUND

The impact of influenza vaccination on major cause-specific hospitalization and the duration of hospital stay is rarely reported. Our purpose was to study the effect of vaccine efficacy on major disease-specific hospitalization and the duration of hospital stays among elderly persons.

SUBJECTS AND METHODS

From 1 January through 30 June 2001, we prospectively observed 35,637 vaccinated elderly persons (age, >or=65 years) and 53,094 unvaccinated elderly persons in Kaohsiung County, Taiwan, by computerized linkage to the National Health Insurance database. Of these persons, 21,347 had been assigned a high-risk status by the Department of Health, Taiwan. Univariate and multivariate logistic regression were used for determining vaccine efficacy in hospitalization. Multiple linear regression analyses were performed for determining the length of hospital stays.

RESULTS

In both high-risk and low-risk groups, vaccination was associated with reducing the rates of hospitalization for all causes (20% vs. 23%), lung diseases, congestive heart failure (43% vs. 32%), renal disease, and liver disease (P<.05). It was also significant for stroke, hypertension, diabetes, neoplasm, and injury in low-risk patients (P<.05). Multivariate logistic regression showed that vaccination was significantly associated with reducing the rate of hospitalization (odds ratio [OR], 0.89; 95% confidence interval [CI], 0.86-0.92), but those with high-risk status had an increased risk of hospitalization (OR, 3.69; 95% CI, 3.56-3.82). Multiple linear regression analysis showed that vaccination decreased the duration of all-cause hospital stays (coefficient, -2.4 days; 95% CI, -2.7 to -2.1 days) and of hospitalization due to lung disease (coefficient, -4.9 days; 95% CI, -6.0 to -3.8 days).

CONCLUSION

Influenza vaccination may reduce hospitalization rates and shorten hospital stays not only for lung diseases but also for other common diseases in high-risk and low-risk elderly populations.