Quantifying the impact of quarantine duration on COVID-19 transmission

Abstract

The numbers of confirmed cases of SARS-CoV-2 infection are increasing in many places. Consequently, the number of individuals placed into quarantine is increasing too. The large number of individuals in quarantine has high societal and economical costs, as well as infringing on the freedom of the individual. This has led to a vigorous debate about the duration of quarantine, particularly in light of the potentially low specificity of quarantine (i.e. low probability of quarantined individuals indeed being infected). We present a mathematical model that leverages empirically determined distributions of incubation period, infectivity, and generation time to quantify how the duration of quarantine affects transmission. With this model we address the impact of shortening the quarantine for returning travellers and traced contacts of confirmed cases, both in terms of prevented transmission and the ratio of prevented transmission to days spent in quarantine. We also consider the impact of i) test-and-release strategies; ii) additional hygiene measures imposed upon release after a negative test; iii) the development of symptoms during quarantine; iv) the relationship between quarantine duration and adherence; and v) the specificity of quarantine. When considering the benefit versus cost utility of quarantine, we find that the diminishing impact of longer quarantine on transmission prevention may support a quarantine duration below 10 days, particularly for returning travellers. A greater gain of utility can be achieved through a test-and-release strategy, and this can be even further strengthened by imposed hygiene measures post-release. We also find that unless a test-and-release strategy is considered, the specificity of quarantine does not affect the optimal duration of quarantine. Therefore, the argument that we should shorten quarantine because of lack of specificity is misguided.

Reducing travel-related SARS-CoV-2 transmission with layered mitigation measures: Symptom monitoring, quarantine, and testing

“…Clifford et al also assessed combined measures and estimated that an 8-day quarantine period with an RT-PCR test on day 7 would be nearly as effective as a 14-day quarantine on its own. Other recent work highlights the effectiveness of shorter quarantine periods combined with testing for individuals with known exposures [46,59,60]. Across these studies, the specific days for quarantine or testing and the estimated effectiveness varied due to differences in assumptions about the time of exposure, different modeled test characteristics, and differences in parameters for the infectious period.…”

“…Data on strategies for reducing risk associated with travel are scant and there are many potential strategies (e.g., the optimal timing of pre-departure or post-arrival testing or the combination of testing and post-arrival quarantine) [36,43–45]. Mathematical models have provided some insights to the potential impact of quarantine combined with testing [44,46]. Here, we build upon those models, considering uncertainty in infectious periods and different testing options to assess a suite of possible combined pre- and post-travel strategies to reduce transmission risk from infected travelers.…”

Optimal test-assisted quarantine strategies for COVID-19

“…A recent, but as yet non-peer-reviewed theoretical study indicates the benefits of COVID-19 tests during quarantine. 6…”

Test-trace-isolate-quarantine (TTIQ) intervention strategies after symptomatic COVID-19 case identification

“…TTIQ strategies are not perfect: each stage in the process is subject to delays and uncertainties and it would be impossible to prevent all onward transmission through TTIQ alone (Ferretti et al, 2020b;Kucharski et al, 2020;Kretzschmar et al, 2020;Quilty et al, 2020;Ashcroft et al, 2020b). Furthermore, in the presence of widespread community transmission the contact tracers may be overwhelmed by the volume of cases.…”

“…In this paper we develop an analytical approach which builds on our previous work in which we have quantified the impact of quarantine duration and high-2 lighted the optimal use of test-and-release strategies (Ashcroft et al, 2020b). Briefly, we use the empirically-observed distributions of transmission timing [Fig.…”