WHO SHOULD BEAR THE COST OF COVID-19 NON-VACCINATION? A LUCK EGALITARIAN ASSESSMENT IN A SOUTH AFRICAN INSURED POPULATION

Background Personal choice in health behaviours raises difficult questions: when individuals freely decline effective preventive interventions, who should bear the resulting costs? This tension is acute in insurance systems where resources are pooled, yet all health systems pursuing Universal Health Coverage must navigate the boundary between collective solidarity and individual accountability. During the COVID-19 pandemic, vaccines were freely available to members of South African private medical schemes, creating conditions in which non-vaccination could plausibly be examined as a matter of personal choice rather than constrained access. This study applied a luck egalitarian framework to assess whether non-vaccination reflected personal choice or constrained circumstance, and to quantify resulting excess costs. Methods A contextual review assessed barriers to vaccination. Using de-identified claims data for approximately 550,000 individuals (March 2020 to December 2022), logistic regression estimated each person's predicted probability of vaccination based on demographic and clinical factors, with observed and predicted rates compared across strata to infer choice versus circumstance. A zero-inflated negative binomial model estimated predicted expenditure among vaccinated members, applied to the full population to simulate universal vaccination. Excess costs were calculated across predicted probability strata. Results Predicted and observed vaccination rates were closely aligned, suggesting that residual non-vaccination in higher-probability groups reflected personal choice rather than constrained circumstance. Observed costs exceeded predicted costs by 22% under universal vaccination, concentrated among older adults and those with comorbidities. Among those with a 60 to 70% predicted probability of vaccination, observed costs exceeded predicted costs by 127.6%. In contrast, among younger, low-risk members, predicted costs slightly exceeded observed expenditure, as vaccination costs were not offset by reduced hospitalisation. Conclusion Risk pooling depends on solidarity, yet non-vaccination due to personal choice shifts costs in ways that challenge fairness in community-rated insurance. These findings highlight the need for transparent deliberation about when personal responsibility should inform equitable health financing design.