Estimating the risk population in relation to influenza vaccination policy.

There are many small differences in national influenza vaccination polices, some are age related and others morbidity related. This study examines a large English general practice database for 2003 to estimate the size of the England and Wales population at risk because of co-morbidity and to make recommendations on the choice of morbidity codes for use when estimating demand for vaccine and in auditing medical records to assess vaccination uptake. Morbidity codes relevant to the assessment of risk were defined and the database was analysed to estimate the annual period prevalence of the various diseases and groups of diseases. A set of morbidity codes is recommended which taken together include 3.2% of age group 0-14 years, 7.5% of 15-44 years and 16.6% of 45-64 years.