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.