BACKGROUND: Policy-makers expect that integration of health and social care will improve user and carer experience and reduce avoidable hospital use. [We] evaluate the impact on emergency hospital admissions of two large nationally-initiated service integration programmes in England: the Pioneer (November 2013 to March 2018) and Vanguard (January 2015 to March 2018) programmes. The latter had far greater financial and expert support from central agencies. METHODS: Of the 206 Clinical Commissioning Groups (CCGs) in England, 51(25%) were involved in the Pioneer programme only, 22(11%) were involved in the Vanguard programme only and 13(6%) were involved in both programmes. We used quasi-experimental methods to compare monthly counts of emergency admissions between four groups of CCGs, before and after the introduction of the two programmes. RESULTS: CCGs involved in the programmes had higher monthly hospital emergency admission rates than non-participants prior to their introduction [7.9 (95% CI:7.8-8.1) versus 7.5 (CI: 7.4-7.6) per 1000 population]. From 2013 to 2018, there was a 12% (95% CI:9.5-13.6%) increase in emergency admissions in CCGs not involved in either programme while emergency admissions in CCGs in the Pioneer and Vanguard programmes increased by 6.4% (95% CI: 3.8-9.0%) and 8.8% (95% CI:4.5-13.1%), respectively. CCGs involved in both initiatives experienced a smaller increase of 3.5% (95% CI:-0.3-7.2%). The slowdown largely occurred in the final year of both programmes. CONCLUSIONS: Health and social care integration programmes can mitigate but not prevent rises in emergency admissions over the longer-term. Greater financial and expert support from national agencies and involvement in multiple integration initiatives can have cumulative effects.