Outcomes
FLU
The pre-registered primary outcome for this study was immunisation uptake by eligible children (i.e. those aged 2 and 3 years on 31st August 2016) at primary care. Anonymised individual-level data was extracted from the CHIS on 28th March 2017. This included flu vaccine history in 2016/17 and 2015/16 flu seasons, age, gender, and GP practice.