Uptake of childhood influenza vaccine from 2012–2013 to 2014–2015 in the UK and the implications for high-risk children: a retrospective observational cohort study

OBJECTIVES To evaluate changes in influenza vaccination rates in healthy and at-risk children following the implementation of the UK's childhood influenza immunisation programme. DESIGN Observational cohort study before and after initiation of the UK's childhood influenza immunisation programme over three influenza seasons (2012-2013, 2013-2014 and 2014-2015) using data from the Clinical Practice Research Datalink (CPRD). SETTING More than 500 primary care practices in the UK. POPULATION All individuals aged 2-17 years on 1 September, with at least 12 months of medical history documented in CPRD were retained in the analysis. INTERVENTION Starting in 2013-2014, all children aged 2 and 3 years were offered influenza vaccination through general practice, and primary school-aged children were offered influenza vaccination in selected counties in England (described as pilot regions). The vaccination programme was extended to all children aged 4 years in England in 2014-2015. MAIN OUTCOME MEASURE Cumulative vaccination rate from 1 September to 28 February of the next calendar year as assessed by a time-to-event statistical model (vaccination uptake). Age group, sex, region and type of high-risk medical condition were assessed as predictors. RESULTS Vaccination uptake increased considerably from 2012-2013 to 2013-2014 in targeted children aged 2-3 years, both in children with a high-risk medical condition (from 40.7% to 61.1%) and those without (from 1.0% to 43.0%). Vaccination rates increased also, though less markedly, in older children. In 2014-2015, vaccination rates remained higher than 40% in healthy children aged 2-3 years, although they decreased slightly from 2013-2014 (from 43.0% to 41.8%). Vaccination rates in older healthy children continued to increase, driven primarily by an increase in children aged 4 years to 31.3% in 2014-2015. CONCLUSIONS The introduction of a universal childhood vaccination policy in the UK increased vaccination rates for targeted children, including those with high-risk conditions.