Background
Universal health coverage (UHC) aims to improve child health through preventive primary care and vaccine coverage. Yet, in many developed countries with UHC, unplanned and ambulatory care sensitive (ACS) hospital admissions in childhood continue to rise. We investigated the relation between preventive primary care and risk of unplanned and ACS admission in children in a high-income country with UHC.

Methods
We followed 319,780 children registered from birth with 363 English practices in Clinical Practice Research Datalink linked to Hospital Episodes Statistics, born between January 2000 and March 2013. We used Cox regression estimating adjusted hazard ratios (HR) to examine subsequent risk of unplanned and ACS hospital admissions in children who received preventive primary care (development checks and vaccinations), compared with those who did not.

Results
Overall, 98% of children had complete vaccinations and 87% had development checks. Unplanned admission rates were 259, 105 and 42 per 1000 child-years in infants (aged < 1 year), preschool (1–4 years) and primary school (5–9 years) children, respectively.

Lack of preventive care was associated with more unplanned admissions. Infants with incomplete vaccination had increased risk for all unplanned admissions (HR 1.89, 1.79–2.00) and vaccine-preventable admissions (HR 4.41, 2.59–7.49). Infants lacking development checks had higher risk for unplanned admission (HR 4.63, 4.55–4.71). These associations persisted across childhood. Children who had higher consulting rates with primary care providers also had higher risk of unplanned admission (preschool children: HR 1.17, 1.17–1.17). One third of all unplanned admissions (62,154/183,530) were for ACS infectious illness. Children with chronic ACS conditions, asthma, diabetes or epilepsy had increased risk of unplanned admission (HR 1.90, 1.77–2.04, HR 11.43, 8.48–15.39, and HR 4.82, 3.93–5.91, respectively). These associations were modified in children who consulted more in primary care.

Conclusions
A high uptake of preventive primary care from birth is associated with fewer unplanned and ACS admissions in children. However, the clustering of poor health, a lack of preventive care uptake, and social deprivation puts some children with comorbid conditions at very high risk of admission. Strengthening immunisation coverage and preventive primary care in countries with poor UHC could potentially significantly reduce the health burden from hospital admission in children.