Evidence of health system resilience in primary health care for preventing under-five mortality in Rwanda and Bangladesh: Lessons from an implementation study during the Millennium Development Goal period and the early period of COVID-19

The coronavirus disease 2019 (COVID-19) pandemic led to disruptions of health service delivery in many countries; some were more resilient in either limiting or rapidly responding to the disruption than others. We used mixed methods implementation research to understand factors and strategies associated with resiliency in Rwanda and Bangladesh, focussing on how evidence-based interventions targeting amenable under-five mortality that had been used during the Millennium Development Goal (MDG) period (2000-15) were maintained during the early period of COVID-19.