Factors associated with uptake of seasonal and pandemic influenza vaccine among clinical risk groups in the UK: an analysis using the General Practice Research Database.

Background: Influenza vaccine uptake rates are low compared with uptake rates of many other vaccines. It is unclear how this differs between risk groups in the population and between pandemic and non-pandemic influenza vaccines.

Aim: This study sought to estimate uptake rates of pandemic and seasonal influenza vaccines among clinical risk groups in the UK during the 2009/2010 influenza season and to identify predictors of vaccine uptake in this cohort.

Methods: Uptake rates were calculated using data from the UK General Practice Research Database (GPRD). Predictors of vaccination were identified using a modified Poisson regression with robust standard error estimates.

Results: Uptake of pandemic influenza vaccine in clinical risk groups was 40.3% and uptake of seasonal influenza vaccine was 61.3%. Factors found to be predictive of seasonal and pandemic influenza vaccination included age and the total number of underlying health conditions an individual had. At risk individuals in those age groups in which universal vaccination of the general population was recommended were more likely to have been vaccinated than individuals in age groups in which only clinical risk groups were recommended for vaccination; hence children in clinical risk groups were more likely to receive pandemic than seasonal influenza vaccine. In older people, having a history of Guillain Barré syndrome was associated with a reduced likelihood of receipt of both seasonal (IRR(adj) 0.83, CI(95) 0.77-0.90) and pandemic influenza vaccines (IRR(adj) 0.82, CI(95) 0.73-0.92).

Discussion: Uptake of pandemic influenza vaccine was lower than that of seasonal influenza vaccine among those at a clinically high risk of influenza related morbidity. This suggests that vaccination strategies may need to be altered during future pandemics. Recommending universal vaccination within age categories in which there is a large proportion of high risk individuals could be considered as this may result in higher uptake among clinical risk groups.