Background: Integrated child health events (ICHEs) are an established and popular mechanism for delivering essential health interventions in low- and middle-income countries (LMICs) suffering resource constraints and health system deficiencies. There is scarce empirical research on whether their expansion and addition of multiple components affect coverage, on the institutional capacities and processes required to support these, and on their implications for routine delivery of immunization. Aim: To examine whether delivering multiple interventions through campaign-style events is an effective strategy in LMICs, given the drive towards expansion of this delivery strategy, and the need to sustain and strengthen routine immunization systems in the long-term. Methods: Guided by an implementation research framework, the study involved a quantitative analysis of a global ICHE dataset, and a qualitative case study of CHWk in Zambia (1999-2014) including semi-structured interviews and document reviews. Zambia represented a unique case as it has consistently relied on campaigns with larger numbers of interventions per event than elsewhere. Findings: ICHEs represented an effective platform with a potential to incorporate multiple key interventions globally without necessarily compromising their coverage. Political stability, government stewardship, high levels of collaborative action and coordination, and the institutionalization of CHWk in Zambia provided a solid base for expansion. Lack of financial and human resources to strengthen district health management fostered a reliance on CHWk to deliver routine immunization. An abrupt top-down policy shift to de-emphasize CHWk, and insufficient local buy-in, in effect obstructed the move towards re-building routine systems. Conclusions: ICHEs continue to play a major role in delivering multiple essential child health interventions in many LMICs. Given their potential to undermine routine immunization systems, a synchronised approach of continued delivery of key services through campaigns in targeted areas, in parallel with strengthening routine delivery, is a viable strategy in pursuing child mortality reductions in the long term.