3. GRADE evidence profile for the effectiveness of quarantine for individuals who were in contact with a confirmed/suspected COVID‐19 case in comparison to no quarantine.

Patient or population: individuals who were in contact with a confirmed or suspected COVID‐19 case Settings: Canada, China, generic population, UK, Republic of Kazakhstan, Singapore, Taiwan, cruise ship Intervention: quarantine Comparison: no quarantine
Outcome	Number of studies	Risk of bias	Indirectness	Imprecision	Inconsistency	Other considerations	Summary effect size/outcome	Certainty of the evidence
Incidence	7 modelling studies (Cao 2020; Hsieh 2007; Koo 2020; Rocklöv 2020; Semenova 2020; Su 2020; Tang 2020a)	Very seriousa	Direct	Precise	Consistent	None	COVID‐19 Cao 2020 simulated the effect of loosening quarantine measures that are already in place. They concluded that if 40% fewer people were quarantined (e.g. because of less strict follow‐ups of contacts), the peak number of cases would increase two‐fold compared to keeping a full quarantine in place. Koo 2020 stated that under the assumption of R0 1.5, at day 80, isolation of infected persons and quarantine of family members reduced the number of infected individuals compared with the baseline scenario by 95.8%. Semenova 2020 simulated that quarantine reduced the number of infected individuals compared with the baseline scenario by 95.8% (2,038,000 versus 84,920). Su 2020 simulated that reducing the quarantine rate for Beijing to 0.8 would lead to 100 more infected cases after 50 days. Decreasing it to 0.6 would lead to approximately 300 more cases. Doubling the quarantine rate would half the number of infected cases. Rocklöv 2020 estimated that isolation and quarantine prevented 2307 (67%) cases during the COVID‐19 outbreak on the Diamond Princess cruise ship. Tang 2020a estimated that without any measures, the number of confirmed COVID‐19 cases in Wuhan would be 7723 by the end of January 2020. They estimated that reduced contact by 50% could reduce the number of confirmed COVID‐19 cases from 7723 to 4335 (44% reduction); reduced contact by 90% could reduce the number of confirmed COVID‐19 cases to 2731 (65% reduction). SARS Hsieh 2007 state that quarantine is effective to reduce incident cases (461 SARS cases (81%) averted, with a low quarantine rate of 0.05 that equals quarantining 1 out of 21 people that should be quarantined)	Low
Onward transmission	5 modelling studies (Kucharski 2020; Liu 2020b; Madubueze 2020; Peak 2020; Rocklöv 2020)	Very seriousa	Direct	Precise	Consistent	None	COVID‐19 Kucharski 2020 estimated that case isolation and quarantine could reduce the effective reproduction number by 37%. Liu 2020b estimated that after implementing quarantine on the Diamond Princess cruise ship the R0 dropped from 6.94 to 0.2 and the transmission rate from 0.026 to 0.0007. Madubueze 2020 estimated R0 to be 1.51 when none of the exposed individuals are quarantined and 0.76 when all exposed individuals are quarantined. Peak 2020 estimated that in a high‐feasibility setting quarantine of individuals can reduce the effective R0 to 0.57 (95% CI 0.32 to 1.05), while monitoring of potentially infected people reduced R0 to 1.55 (95% CI 0.65 to 2.7) assuming a larger fraction of presymptomatic infections. In a low‐feasibility setting, both individual quarantine and active control monitoring alone could not reduce the R0 below 1 for both serial interval scenarios. Rocklöv 2020 estimated that isolation and quarantine lowered the R0 from 14.8 to 1.78 during the COVID‐19 outbreak on the Diamond Princess cruise ship.	Low
Mortality	3 modelling studies (Ferguson 2020; Hsieh 2007; Semenova 2020)	Very seriousa	Direct	Precise	Consistent	None	COVID‐19 Ferguson 2020 estimated that for a timeframe of 3 months, case isolation and household quarantine would reduce deaths in the UK by 31% to 34%. Semenova 2020 simulated that quarantine reduced the number of deaths compared with the baseline scenario by 75.8% (15,470 versus 3750). SARS Quarantine was effective in reducing mortality (62 SARS (63%) deaths averted, with a low quarantine rate of 0.05 in Taiwan (Hsieh 2007))	Low
Costs	3 modelling studies (Gupta 2005; Mubayi 2010; Semenova 2020)	Very seriousa	Indirectb	Precise	Consistent	None	COVID‐19 Semenova 2020 states that the introduction of quarantine may potentially reduce the number of ICU doctors and nurses needed to 500 (from 12,026 without quarantine) and 2420 (from 58,144) meaning fewer resources required and lower costs in the healthcare sector. SARS Gupta 2005 stated that at a transmission rate of 8%, the total savings of quarantine over isolation alone varies between CAD 279 million to 232 million (reference year 2003). The earlier that effective quarantine measures are implemented, the greater are the savings. Mubayi 2010 came to similar conclusions and stated that increasing the quarantine effort results in lower overall costs over the entire outbreak in all 3 assessed quarantine strategies.	Very low
CAD: Canadian Dollar; COVID‐19: coronavirus disease 2019;ICU: intensive care unit; R0: basic reproduction number; SARS: severe acute respiratory syndrome

^aDowngraded two steps for risk of bias: one because we had moderate to minor concerns regarding quality and one because model parameters are accompanied by uncertainties.
^bDowngraded one step for indirectness because studies were on SARS or (in COVID‐19 study) only one aspect of resource use (health care personnel) was mentioned, without mentioning costs of quarantine measures.