Vaccine Hesitancy as a Systems-Level Vulnerability: Historical Evolution, Sociopolitical Drivers, and Implications for Immunization Resilience

Vaccine hesitancy has evolved from episodic resistance to a structural threat to global health systems. Although opposition to vaccination has accompanied immunisation since its inception, contemporary hesitancy reflects a transformation driven by digital information ecosystems, political polarisation, institutional mistrust, and shifting risk perceptions. Its consequences extend beyond individual vaccine refusal to systemic vulnerabilities within immunisation programs. Here, wesynthesisee historical and contemporary evidence to examine vaccine hesitancy as a multilevel phenomenon shaped by sociocultural identities, psychological heuristics, and political governance structures. Tracing its trajectory from early smallpox resistance to COVID-19–era polarization, we identify recurring patterns of mistrust, moral framing, and autonomy-based resistance that re-emerge across contexts. We argue that vaccine hesitancy operates not merely as an attitudinal deficit but as a reflection of broader fractures in social trust and institutional legitimacy. We further analyse how clustering of under-immunised populations, digital misinformation amplification, and politicisation of public health undermine immunisation resilience. Evidence suggests that durable solutions require trust-centred governance, community co-production of health strategies, behavioral insight informed communication, and structural reforms that address inequity and historical injustice. Reconceptualising vaccine hesitancy as a systems-level vulnerability reframes immunisation programs as social contracts as much as biomedical interventions. Strengthening these contracts will be central to sustaining global vaccination gains in an era defined by misinformation, institutional fragility, and recurrent pandemic threats.