Intersectional inequalities in COVID-19 hospitalisation and mortality: A nationwide MAIHDA study of Swedish adults across four pandemic waves (2020–2022)

Background: COVID-19 has been described as a syndemic shaped by interactions between viral exposure, co-morbidities, and social inequalities. However, much of the literature relies on single-axis analyses and restricted time horizons, obscuring how health inequalities shifted across pandemic phases. Intersectionality theory conceptualises how social positions intersect within systems of power to produce context-dependent inequalities. Nationwide intersectional evidence on health inequalities across the full pandemic remains scarce. Methods: Drawing on intersectionality methodology, we conducted a nationwide register-based cohort study of all Swedish adults (≥18 years) from March 2020 to March 2022. Intersectional strata combined sex, income, education, and birthplace income classification. COVID-19 hospitalisation and mortality were analysed separately for younger (18–69 years) and older (≥70 years) adults across four waves using multilevel models (MAIHDA) capturing between- and within-stratum heterogeneity. Results: Sweden recorded 67,997 COVID-19 hospitalisations and 15,895 deaths. Single-axis analyses indicated higher risks among men, those with lower education, and migrants from lower-income countries. Intersectional analyses revealed substantial heterogeneity and temporal variation. Among younger adults, intersectional strata accounted for up to 25% of variation in mortality. Among LIC-born men aged ≥70, wave-1 mortality was nearly fourfold higher in the low-income/low-education stratum that in the high-income/high-education stratum. Among older high-income men, hospitalisation disparities between LMIC-born and Swedish-born strata narrowed substantially across educational levels, with only small differences remaining by wave 4. Conclusions: Inequalities in severe COVID-19 outcomes were intersectional and temporally dynamic. The findings highlight the importance of moving beyond static, single-axis approaches to understand evolving health inequalities and inform equity-oriented pandemic preparedness and response.