Improving the timeliness and equity of preschool childhood vaccinations: Mixed methods evaluation of a quality improvement programme in primary care

Background: We conducted a mixed methods evaluation to assess whether implementing a primary care quality improvement (QI) programme utilising a digital call-and-recall tool improved timely receipt and equity of first measles, mumps and rubella (MMR) and diphtheria tetanus, pertussis and polio-containing (DTaP /IPV) vaccinations. Methods: 138,133 and 136,952 children were eligible to receive first MMR and DTaP/IPV respectively between 1st January 2019 and 31st January 2024 in North East London. We compared proportions with timely first MMR or DTaP/IPV receipt (by ages 18 and six months respectively) pre- and post-implementation using an interrupted time series analysis. We calculated change in the Slope Index of Inequality (SII) by an area-level deprivation measure. We conducted 'Think Aloud' exercises and semi-structured interviews with users. Findings: The proportion of children with timely first MMR receipt increased by 5.3 % (Rate Ratio [RR]:1.053, 95 % confidence interval [CI]:1.033-1.073), equating to an absolute increase in timely MMR receipt of 4.1 %- from 77.7 % to 81.8 %- and for first DTaP/IPV by 0.9 % (RR:1.009, 95 % CI:1.003-1.015). There was no significant change in SII for either vaccine. Users reported improved recall with tool use, but identified practice-level and systemic barriers, including staff dynamics and unachievable national targets, limiting its consistent use. Interpretation: In a real-world setting, a call-and-recall tool within a primary care QI programme improved timely first MMR receipt. Sustained improvement requires additional support including by incentivising achievable targets and improving staff capacity and training. Funding: National Institute of Health and Care Research; Barts Charity.