To estimate the impacts of demographic factors and income disparities on the case fatality rate (CFR) of COVID-19 in Hong Kong, taking into account the influence of reporting delays (ie, the duration between symptom onset and case confirmation).

Retrospective observational longitudinal study.

A total of 7406 symptomatic patients with residence information reported between 23 January 2020 and 2 October 2021.

The study examined the disparity in COVID-19 deaths associated with the factors such as age (≥65 vs 0–64 years old groups), gender and the income level of districts (low income vs non-low income). The severe reporting delay (>10 days) was considered as the mediator for mediation analysis. A Cox proportional hazards regression model was constructed.

We found that CFR was 3.07% in the low-income region, twofold higher than 1.34% in the other regions. Although the severe reporting delay was associated with a hazard ratio (HR) of about 1.9, its mediation effect was only weakly present for age, but not for gender or income level. Hence, high CFR in Hong Kong was largely attributed to the direct effects of the elderly (HR 25.967; 95% CI 14.254 to 47.306) and low income (HR 1.558; 95% CI 1.122 to 2.164).

The disparity in COVID-19 deaths between income regions is not due to reporting delays, but rather to health inequities in Hong Kong. These risks may persist after the discontinuation of test-and-trace measures and extend to other high-threat respiratory pathogens. Urgent actions are required to identify vulnerable groups in low-income regions and understand the underlying causes of health inequities.