The effectiveness of national influenza vaccination policies for at-risk populations over 5 seasons in a Scottish general practice.

AIM: To determine the effectiveness of serial influenza vaccination. SCOPE: Studied in a Scottish GP population, the overall seroresponse rate increased with annual influenza vaccinations and after 5 years it increased from 45.1% to 93.3% for influenza virus A (H1) and from 48.4% to 98.3% for influenza virus A (H3). However, there was little boosting effect with further doses after becoming a seroresponder. The pre-vaccination titres were significantly higher in previous year's seroresponders compared to non-responders. CONCLUSIONS: The policy of annual vaccination is supported by our data in order to increase the disappointing response rate after one dose. However, the lack of a boosting response with subsequent doses and the significant residual immunity after becoming a seroresponder suggests a prior serological immunity check in order to better direct the vaccine supply (in the years of no antigenic drift), to those who need it most.