The Dutch influenza vaccination policy and medication use, outpatient visits, hospitalization and mortality at age 65

Background: Our objective was to obtain estimates of the impact of the Dutch vaccination programme on medication use, outpatient visits, hospitalization and mortality at age 65. Methods: We linked population-wide mortality, hospitalization and municipality registries to identify influenza-related deaths and hospitalizations, and used health interview surveys to identify medication use and outpatient visits during 1996-2008. We applied a regression discontinuity design to estimate the intention-to-treat effect of the personal invitation for a free influenza vaccination sent to every Dutch inhabitant at age 65 years on each of the outcomes, separately in influenza-epidemic and non-epidemic months. Results: Invitation receipt for free influenza vaccination at age 65 led to a 9.8 percentage points [95% confidence interval (CI) = 3.5 to16.1; P<0.01] rise in influenza vaccination. During influenza-epidemic months, it was associated with 1.5 fewer influenza/pneumonia deaths per 100 000 individuals (95% CI = -3.1 to -0.0; P = 0.05), a 15 percentage point lower probability to use prescribed medicines (95% CI = -28 to -3; P = 0.02) and 0.13 fewer General Practitioner (GP) visits per month (95% CI = -0.28 to 0.02; P = 0.09), while the association with hospitalizations due to influenza/pneumonia was small and imprecisely estimated (seven more hospitalizations per 100 000 individuals, 95% CI = -20 to 33; P = 0.63). No associations were found with any outcomes during non-epidemic months. Conclusions: Personal invitations for a free influenza vaccination sent to every Dutch inhabitant at age 65 took pressure off primary health care but had small effects on hospitalizations and mortality.