Using serial cross-sectional anti-nucleocapsid seroprevalence data from Canadian Blood Services donors (April 2021–April 2023), this study assessed whether seroprevalence convergence across socioeconomic strata truly reflected reduced SARS-CoV-2 infection risk, or masked persistent disparities in force of infection by area-level material deprivation quintile.
Pre-Omicron, the most deprived quintile (Q5) had a 71% higher force of infection than the least deprived (Q1; IRR 1.71, 95% CI 1.60–1.83). After Omicron, relative disparity compressed (Q5 vs Q1 IRR: 1.12, 95% CI 1.11–1.14) due to disproportionate amplification in less-deprived groups (48.5-fold increase in Q1 vs 31.8-fold in Q5), but Q5 continued to have the highest absolute infection rate throughout.
- Blood donors are not representative of the general population, potentially introducing selection bias in seroprevalence estimates. - Area-level material deprivation is an ecological proxy and may not capture individual-level socioeconomic variation. - The model assumes a sero-reversion framework; unmeasured heterogeneity in antibody waning across deprivation strata could affect estimates.
Seroprevalence convergence across income groups should not be interpreted as equity in infection risk — lower-income communities continued to face higher absolute SARS-CoV-2 exposure even during Omicron. Public health interventions targeting socioeconomically deprived populations remain warranted even when aggregate surveillance data appear to show parity.
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