Investigating COVID-19 transmission and mortality differences between indigenous and non-indigenous populations in Mexico

Abstract

Objectives: Indigenous populations have been disproportionately affected during pandemics. We investigated COVID-19 mortality estimates among indigenous and non-indigenous populations at national and sub-national levels in Mexico.

Methods: We obtained data from the Ministry of Health, Mexico, on 2,173,036 laboratory-confirmed RT-PCR positive COVID-19 cases and 238,803 deaths. We estimated mortality per 1000 person-weeks, mortality rate ratio (RR) among indigenous vs. non-indigenous groups, and hazard ratio (HR) for COVID-19 deaths across four waves of the pandemic, from February 2020 to March 2022. We also assessed differences in the reproduction number (R_t).

Results: The mortality rate among indigenous populations of Mexico was 68% higher than that of non-indigenous groups. Out of 32 federal entities, 23 exhibited higher mortality rates among indigenous groups (P < 0.05 in 13 entities). The fourth wave showed the highest RR (2.40). The crude HR was 1.67 (95% CI: 1.62, 1.72), which decreased to 1.08 (95% CI: 1.04, 1.11) after controlling for other covariates. During the intense fourth wave, the R_t among the two groups was comparable.

Conclusion: Indigenous status is a significant risk factor for COVID-19 mortality in Mexico. Our findings may reflect disparities in non-pharmaceutical (e.g., handwashing and using facemasks), and COVID-19 vaccination interventions among indigenous and non-indigenous populations in Mexico.

Keywords: COVID-19 mortality; Disparity; Hazard Ratio; Indigenous; Mexico; Reproduction number.

Figure 1

Flowchart showing the inclusion of cases and deaths in the study.

Figure 2

(A.) Daily incidence of COVID-19 cases among non-indigenous from 19 February 2020 - 25 March 2022 (B.) Time-varying R_t of COVID-19 cases among non-indigenous populations for the study period (C.) Mean R_t for the early ascending phase of four waves among non-indigenous (30 days from 5 April 2020 - 4 May 2020 for first wave, 30 days from 29 September 2020 – 28 October 2020 for second wave, 30 days from 27 June 2021 - 26 July 2021 for the third wave and 15 days from 23 December 2021 - 6 January 2022 for the fourth wave) (D.) Daily incidence of COVID-19 cases among Indigenous from 19 February 2020 -25 March 2022 (E.) Time-varying R_t of COVID-19 cases among indigenous populations for the study period (F.) Mean R_t for the early ascending phase of four waves among indigenous (30 days from 15 April 2020 - 14 May 2020 for first wave, 30 days from 15 November 2020 - 14 December 2020 for second wave, 30 days from 11 July 2021 - 9 August 2021 for the third wave and 15 days from 27 December 2021 - 10 January 2022 for the fourth wave). Dates indicate date of symptom onset. The shaded gray areas in B, C, E and F indicate 95% CrL. CrL, credible interval; R_t, reproduction number

Figure 3

COVID-19 mortality rate per 1000 person-weeks in indigenous and non-indigenous populations in Mexico, February 2020 to March 2022.

Figure 4

Rate ratio (RR) of COVID-19 mortality per 1000 person-weeks among indigenous and non-indigenous populations by federal entities in Mexico.

Figure 5

Survival curves for hospitalized and outpatient COVID-19 cases among indigenous and non-indigenous groups.