Who remains uncovered? Assessing inequalities and determinants of national health insurance enrolment among informal sector workers in Kenya

Abstract Background Many sub-Saharan African countries are increasingly adopting national health insurance policies to improve access to essential services. Informal sector workers, however, often lack coverage because their earnings are typically not low enough to qualify for government subsidies but insufficient to cover insurance premiums, resulting in a phenomenon known as "missing middle". This paper examined socioeconomic inequalities in national health insurance enrolment and determinants of participation among informal sector workers in Kenya. Methods We used nationally representative cross-sectional household survey data (n = 5168) collected from informal sector workers in Kenya in December 2020. First, we examined levels of national health insurance enrolment among informal sector workers. Second, we examined socioeconomic inequalities in national health insurance enrolment using concentration curves and the Wagstaff index. Third, we employed a three-level mixed effects logistic regression model to assess the determinants of national health insurance enrolment. Results Overall, 21.75% (95% Confidence Interval 20.63–22.89) of informal sector workers in Kenya were enrolled in the national health insurance scheme. We observed pro-rich inequalities in national health insurance enrolment, with a concentration index of 0.35 (95% CI 0.30–0.41). Older age (adjusted odds ratio (AOR) = 1.66, 95% CI 1.31–2.10), employment in the non-agricultural sector (AOR = 1.96, 95% CI 1.60–2.39), microfinance institutional membership (AOR = 1.44, 95% CI 1.23–1.69), higher education level (AOR = 2.49, 95% CI 1.99–3.11), household’s prior positive experience with healthcare (AOR = 1.45, 95% CI 1.22–1.72), and higher socioeconomic status based on the wealth asset index (AOR = 3.87, 95% CI 2.97–5.05) were all significantly positively associated with national health insurance enrolment. Larger households had lower odds of enrollment (AOR = 0.76, 95% CI 0.60–0.96). Conclusions Our findings suggest that enrollment rates among informal sector workers remain low, and important pro-rich inequalities prevail. Economic factors, education, and prior experience with healthcare services were key drivers of national health insurance enrollment. Further policies are needed to increase enrollment among informal sector workers, including differential premium levels, reliance on expanded targeted subsidies, and enhanced awareness campaigns. Our findings are also applicable to other low-resource settings experiencing conditions similar to those in Kenya as they transition toward national health insurance policies, with the goal of achieving universal health coverage.