Background: A significant cause of morbidity and mortality in the United States is infection secondary to influenza A and B viruses. These viruses are associated with the seasonal increase of influenza and pneumonia diagnoses, hospitalizations, and exacerbations of underlying chronic diseases. The primary prevention against influenza is annual vaccination. Studies have shown that influenza vaccination reduces all-cause mortality and hospitalizations in older persons and decreases work absences in younger persons. Other vaccines have been shown to provide attenuation of other illnesses, but influenza vaccine has not been evaluated concerning this issue. Spaude and colleagues assessed the effect of previous influenza immunization on outcomes in adults with community-acquired pneumonia.

The Study: The four-year study included adults admitted to one health care system during each influenza season (November through April) with the diagnosis of community-acquired pneumonia. Data collected on admission were age, sex, medical history, nursing home residency, vital signs, clinical and radiographic findings, and laboratory values. The data were used to calculate the Pneumonia Outcome Research Team (PORT) score, which is a 5-point scale that predicts pneumonia outcomes. Patients who score 4 or 5 on the PORT scale are at significantly higher risk of in-hospital death. Information about influenza and pneumococcal vaccinations also was collected. The main outcome measure was in-hospital mortality.

Results: From 34 participating hospitals, 17,393 persons met the inclusion criteria. Of those with recorded vaccination status, 1,590 patients (19 percent) had received an influenza vaccination in the current or most recent influenza season. Those who reported receiving the vaccination were significantly less likely to die in the hospital of any cause than those who did not receive it (odds ratio = 0.30; 95% confidence interval, 0.22 to 0.41). After adjusting for the presence of other comorbidities and pneumococcal vaccination, this outcome remained significant. The reduction of all-cause mortality occurred in those with high or low PORT scores.

Conclusion: Influenza vaccination was shown to improve survival rates in patients hospitalized during the influenza season with community-acquired pneumonia. The authors add that this information, if confirmed by other studies, could be used to improve vaccination rates in adults at risk of community-acquired pneumonia.