Influenza vaccine effectiveness in preventing ambulatory care among the elderly under NHI in Taiwan

Objectives. The benefits of influenza vaccination in preventing hospitalizations among the elderly aged over 65 were well known in literature, but little is discussed about the effectiveness in preventing ambulatory care. Taiwan's CDC provided free influenza vaccination for all elderly people through the National Health Insurance program in 2002. In this study we examined the influenza vaccination effectiveness in ambulatory care.

Methods. Retrospective cohort study was conducted by using a random cohort of 15,024 elderly in 2002 from the claims data of Taiwan's NHI program. Two-part model was used to estimate the effectiveness of the vaccine in the period of influenza vaccine validity for the prevention of ambulatory care for related ambulatory care after adjustment for important covariates included demographic characteristics, co-morbidities and prior utilizations.

Results. Although the providence of influenza vaccination was free, there were only 51 % elderly people reached to the vaccination. The vaccination participants had more yearly outpatient utilization in visit number (29 vs. 21) and in expenditure ( NTD 30538 vs.23752) then those elderly people without vaccination. However, there were no significant differences in utilization of ambulatory care for pneumonia, influenza, congestive heart failure, and for all-cause ambulatory care when the elderly sought to health care under the 2nd part model analysis.

Conclusions. This results revealed that the vaccination participants did not use more ambulatory care in the period of influenza vaccine validity, although they tending to have worse health status and having more health utilization. Influenza vaccination creates important external benefit under universal NHI.