Strengthening national disaster management legislation and policy is critical for preventing and reducing catastrophic health effects from the growing threat of natural hazard disasters. Although evaluations of the effectiveness of legal and policy instruments are rarely published, similar approaches continue to be applied universally by governments to align their response to disaster impacts. This study analyzed and contrasted the effect of disaster legislation and policy on the emergency health and medical response to six complex natural hazard disasters, including typhoon, earthquake, flood, smoke haze, thunderstorm asthma and the COVID-19 pandemic.

The study applied qualitative multi-case study methodology and used a standardized program logic model to synthesize and analyze the effect of national disaster legislation and policy on emergency health and medical responses. Events were case-bounded by date, more than 9,000 casualties, and local emergency responses provided health and medical care.

Four themes emerged critical to health system response. Where legislation and policy provided clear separation of powers, systems delineated roles and responsibilities, provided clarity and process for assessment, resource acquisition, and operational mandates. Policies that created dedicated local networks and included non-health related organizations, accelerated coordination of crucial health functions for rapid mobilization and prioritization for affected populations. In all but one case, the hazard was closely monitored, already affected communities, and catastrophic risk to life understood, before the declaration and statutory powers were invoked.

Using ‘declarations’ as the legal instrument to initiate ‘whole of government’ resources in disasters requires urgent review, especially where advanced hazard monitoring systems exist. Disaster and emergency health policy should support action orientated toward exposure mitigation, inclusion of non-traditional health actors and partnership building. International policy mechanisms are required to address emerging health threats not locally prioritized and advance regional cooperation agreements when the impact of hazards harm populations outside geographic boundaries.