Low-impact social distancing interventions to mitigate local epidemics of SARS-CoV-2

Abstract

Many jurisdictions implemented intensive social distancing to suppress SARS-CoV-2 transmission. The challenge now is to mitigate the ongoing COVID-19 epidemic without overburdening economic and social activities. An agent-based model simulated the population of King County, Washington. SARS-CoV-2 transmission probabilities were estimated by fitting simulated to observed hospital admissions. Interventions considered included encouraging telecommuting, reducing contacts to high-risk persons, and reductions to contacts outside of the home, among others. Removing all existing interventions would result in nearly 42,000 COVID-19 hospitalizations between June 2020 and January 2021, with peak hospital occupancy exceeding available beds 6-fold. Combining interventions is predicted to reduce total hospitalizations by 48% (95% CI, 47-49%), with peak COVID-19 hospital occupancy of 70% of total beds. Targeted school closures can further reduce the peak occupancy. Combining low-impact interventions may mitigate the course of the COVID-19 epidemic, keeping hospital burden within the capacity of the healthcare system.

Keywords: Biological; COVID-19; Herd; Immunity; Models; SARS-CoV-2.

Fig. 1

Observed vs. simulated hospital admissions for COVID-19 – King County Washington, February–May 2020. Panel A, admissions by date; Panel B, admissions by age group. 95% confidence intervals are indicated by shaded region (panel A) or by vertical range lines (panel B).

Fig. 2

Hypothetical daily COVID-19 hospital admissions under individual mitigation strategies vs. no intervention (black lines) – King County, February–June 2020. Shaded regions indicate 95% confidence intervals.

Fig. 3

Expected number of hospital beds occupied by COVID-19 patients under cumulative intervention scenarios – King County, June 2020–January 2021. Shaded regions indicate 95% confidence intervals.

Fig. 4

Expected proportion of hospital beds occupied by COVID-19 patients using combined interventions with or without short-term school closures – King County, June 2020–January 2021. Shaded regions indicate 95% confidence intervals.