Comparison of infection control strategies to reduce COVID-19 outbreaks in homeless shelters in the United States: a simulation study

Table 2 Probability of averting an outbreak over a 30-day period in a generalized homeless shelter with simulated infection control strategies

Infection control strategy^‡	Probability of averting an outbreak (UR)^§
Infection control strategy^‡	R₀ = 1.5 (low-risk)	R₀ = 2.9 (Seattle)	R₀ = 3.9 (Boston)	R₀ = 6.2 (San Francisco)
1) Symptom screening	0.35 (0.21–0.67)	0.13 (0.05–0.39)	0.08 (0.02–0.28)	0.04 (0.00–0.15)
2) Routine twice-weekly PCR testing	0.53 (0.34–0.87)	0.20 (0.10–0.64)	0.12 (0.05–0.50)	0.09 (0.01–0.33)
3) Universal mask wearing	0.62 (0.26–0.99)	0.27 (0.07–0.94)	0.19 (0.04–0.90)	0.08 (0.01–0.77)
4) Relocation of high-risk individuals	0.33 (0.20–0.68)	0.13 (0.05–0.40)	0.07 (0.02–0.29)	0.04 (0.00–0.15)
5) Routine twice-weekly PCR testing of staff only	0.41 (0.28–0.72)	0.15 (0.07–0.40)	0.09 (0.03–0.33)	0.04 (0.01–0.17)
6) Combination strategy	0.74 (0.40–1)	0.42 (0.13–0.99)	0.29 (0.07–0.97)	0.19 (0.02–0.91)

Outbreak is defined as ≥3 infections originating within the shelter in any 14-day period
Generalized homeless shelter defined as 250 residents and 50 staff with a background infection rate estimated from data for Boston (~ 120/1,000,000 person-days)
See Additional file 1: Table S9 and Fig. 1 for the results for other background infection rates and Additional file 1: Table S10 for the reductions in infections and symptomatic cases. See Additional file 1: Figures S6–S8 for the outbreak size distributions for the different R₀ values
UR uncertainty range, R₀ basic reproduction number
^‡All strategies included daily symptom screening
^§UR generated from parameter sensitivity analysis (see Table 1 and Additional file 1)

ISSN: 1741-7015