Dependence of COVID-19 Policies on End-of-Year Holiday Contacts in Mexico City Metropolitan Area: A Modeling Study

Abstract

Background. Mexico City Metropolitan Area (MCMA) has the largest number of COVID-19 (coronavirus disease 2019) cases in Mexico and is at risk of exceeding its hospital capacity in early 2021. Methods. We used the Stanford-CIDE Coronavirus Simulation Model (SC-COSMO), a dynamic transmission model of COVID-19, to evaluate the effect of policies considering increased contacts during the end-of-year holidays, intensification of physical distancing, and school reopening on projected confirmed cases and deaths, hospital demand, and hospital capacity exceedance. Model parameters were derived from primary data, literature, and calibrated. Results. Following high levels of holiday contacts even with no in-person schooling, MCMA will have 0.9 million (95% prediction interval 0.3-1.6) additional COVID-19 cases between December 7, 2020, and March 7, 2021, and hospitalizations will peak at 26,000 (8,300-54,500) on January 25, 2021, with a 97% chance of exceeding COVID-19-specific capacity (9,667 beds). If MCMA were to control holiday contacts, the city could reopen in-person schools, provided they increase physical distancing with 0.5 million (0.2-0.9) additional cases and hospitalizations peaking at 12,000 (3,700-27,000) on January 19, 2021 (60% chance of exceedance). Conclusion. MCMA must increase COVID-19 hospital capacity under all scenarios considered. MCMA's ability to reopen schools in early 2021 depends on sustaining physical distancing and on controlling contacts during the end-of-year holiday.

Keywords: COVID-19; Mexico; dynamic transmission model; hospital capacity; non-pharmaceutical interventions.

Figure 1

Observed (red dots) and model-predicted (green lines) COVID-19 incident detected cases (A), deaths (B), cumulative cases (C), and deaths (D) in MCMA between February 24, 2020, and March 7, 2021. Left column plots assume compliance with physical distancing during the end-of-year holiday period. Right column plots assume substantially less compliance with physical distancing during the end-of-year holiday period. The double-dashed vertical line represents the last day used for calibration. The green shaded area shows the 95% posterior model-predictive interval of the outcomes, and the green lines show the posterior model-predicted mean based on 1,000 simulations using samples from the posterior distribution.

Figure 2

Observed (red area) and model-predicted (green lines) total hospital occupancy and demand in MCMA between February 24, 2020, and March 7, 2021. The left plot assumes compliance with physical distancing during the end-of-year holiday period. The right plot assumes substantially less compliance with physical distancing during the end-of-year holiday period. The double-dashed vertical line represents the last day used for calibration. The green shaded area shows the 95% posterior model-predictive interval of the outcomes, and the colored lines show the posterior model-predicted mean based on 1,000 simulations using samples from the posterior distribution. The horizontal black lines show total COVID-19-specific hospital capacity.

Figure 3

Estimated model-predicted daily incident cases (A) and deaths (B) by scenario in MCMA between December 7, 2020, and March 7, 2021. Left column plots assume compliance with physical distancing during the end-of-year holiday period. Right column plots assume substantially less compliance with physical distancing during the end-of-year holiday period. The vertical dashed line represents the day of policy implementations.

Figure 4

Estimated model-predicted daily hospitalization demand in MCMA between December 7, 2020, and March 7, 2021. The left column plots assume compliance with physical distancing during the end-of-year holiday period. The right column plots assume substantially less compliance with physical distancing during the end-of-year holiday period.

Figure 5

Daily estimated probability of hospitalization demand exceeding COVID-19-specific capacity in MCMA between December 7, 2020, and March 7, 2021, by levels of compliance with physical distancing during the end-of-year holiday period. The top panel assumes compliance with physical distancing during the end-of-year holiday period. The bottom panel assumes substantially less compliance with physical distancing during the end-of-year holiday period.