Determining quarantine length and testing frequency for international border opening during the COVID-19 pandemic

Abstract

Background The COVID-19 pandemic has resulted in the closure or partial closure of international borders in almost all countries. Here we investigate the efficacy of imported case detection considering quarantine length and different testing measures for travellers on arrival. Methods We examine 8 broad border control strategies from utilising quarantine alone, pretesting, entry and exit testing, and testing during quarantine. In comparing the efficacy of these strategies, we calculate the probability of detecting travellers who have been infected up to 2 weeks pre-departure according to their estimated incubation and infectious period. We estimate the number of undetected infected travelers permitted entry for these strategies across a prevalence range of 0.1%–2% per million travelers. Results At 14-day quarantine, on average 2.2% (Range: 0.5%–8.2%) of imported infections are missed across the strategies, leading to 22 (5–82) imported cases at 0.1% prevalence per million travellers, increasing up to 430 (106–1641) at 2%. The strategy utilising exit testing results in 3.9% (3.1%–4.9%) of imported cases being missed at 7-day quarantine, down to 0.4% (0.3%–0.7%) at 21-day quarantine, and the introduction of daily testing, as the most risk averse strategy, reduces the proportion further to 2.5%–4.2% at day 7 and 0.1–0.2% at day 21 dependent on the tests used. Rapid antigen testing every 3 days in quarantine leads to 3% being missed at 7 days and 0.7% at 14 days, which is comparable to PCR testing with a 24-hour turnaround. Conclusions Mandatory testing, at a minimal of pre-testing and on arrival, is strongly recommended where the length of quarantining should then be determined by the destination country’s level of risk averseness, pandemic preparedness and origin of travellers. Repeated testing during quarantining should also be utilised to mitigate case importation risk and reduce the quarantining duration required.

Effects of adjusting public health, travel, and social measures during the roll-out of COVID-19 vaccination: a modelling study

“…23 Our estimate of 60-65% is also consistent with the results from a previous modelling study. 24 In the worst-case scenario wherein infected travellers are infected right before arrival, testing upon arrival without quarantine would have no effect on their FOI because their viral load upon arrival would be below the detection threshold. Fully vaccinated inbound travellers would have their expected FOI lowered by σ m due to the vaccine reducing their susceptibility to infection.…”

International Travel-Related Control Measures to contain The Covid-19 Pandemic: An update to a Cochrane Rapid Review

“…Two modelling studies on microbiological detection (10, 14) were identified in the updated search. Assuming that exposure had occurred, pre-departure testing was predicted to improve the detection of cases by up to 84.4%, although results vary according to timing of the test.…”

“…Two modelling studies (9, 10) demonstrated that a combination of quarantine and microbiological detection with a PCR test at day 7 significantly increases the proportion of cases averted as compared with quarantine alone, thus reducing the quarantine period.…”

“…The updated search identified nine modelling studies (7)(8)(9)(10)(11)(12)(13)(14)(15) and eight observational studies (16)(17)(18)(19)(20)(21)(22)(23).…”

The Experience of Hotel Quarantine During Omicron Variant of COVID-19

“…In this regard, mandatory testing before the travel and on arrival has been recommended by many governments; and the length of the quarantine can be determined according to the results of the tests. Moreover, the risk level of the destination and the travelers' origin can be influential (8). In spite of this evidence about the flexibility in the period of quarantine, some other federal or local governments insist on applying 14-day quarantine for international travelers.…”