Summary of findings 4. Quarantine and screening at borders.

Disease: COVID‐19 Interventions: implementing quarantine and screening measures combined Comparators: implementing a single measure of quarantine or screening
Outcome	Number of studies	Summary of findings	Certainty of evidence
Outcome category: cases avoided due to the measure
No contributing study.
Outcome category: shift in epidemic development
Time to outbreak	1 modelling study	The study reported delays in outbreak resulting from combination of screening and quarantine compared with a single measure. Under the assumption of one flight per day (7.1% of normal travel volume) and 50% sensitivity of screening, the time to outbreak would vary greatly for different combinations of measures ranging from 3.5 years (95% CI 0.09 to 12.9) to 34.1 years (95% CI 0.86 to 126) to outbreak.	Very low a,b,c ⨁◯◯◯
Outcome category: cases detected due to measure
Days at risk of transmitting the infection into the community	2 modelling studies	Both studies reported that the combination of quarantine and testing would reduce days that travellers, upon release, remain at risk of transmitting the infection into the community compared with a single measure. These positive effects ranged from 0.01 fewer days to 2.0 fewer days at risk of transmission.	Low b,c ⨁⨁◯◯
Probability of releasing an infected individual into community	3 modelling studies	All studies reported positive effects resulting from a combination of screening and quarantine. These positive effects included a reduction in the probability of releasing an infected individual ranging from 2% to 48%. The variation in the magnitude of effect could be explained by the length of the quarantine period, day(s) on which the test is conducted in quarantine or the risk of transmission within quarantine.	Very lowb,c,d ⨁◯◯◯
Proportion of cases detected	2 modelling studies	Both studies reported that the combination of quarantine and testing would further increase case detection compared with single measures. These positive effects ranged from 41% to 99% of cases detected. The variation in the magnitude of effect may be explained by the length of the quarantine period with longer quarantine and the duration of travel and stay in the country of departure.	Very low b,c,e ⨁◯◯◯
Proportion of cases detected	4 observational studies	All studies reported that the combination of quarantine and testing would further increase case detection compared with single measures. The proportion of cases detected ranged from 68.8% to 90.2%. The type of initial exit and/or entry screening could play a role; while most employed a PCR test upon arrival, one study employed symptom screening. Whether travellers in quarantine were monitored for the development of symptoms, and the intensity of this monitoring may also have been important.	Lowb,f ⨁⨁◯◯

^aDowngraded ‐1 for risk of bias, due to major quality concerns in some studies related to the appropriateness of the model’s structural assumptions, the input parameters, and the adequacy of assessment of the model’s uncertainty.

^bDowngraded ‐1 for imprecision, due to a wide range of plausible effects.

^cDowngraded ‐1 for indirectness, due to no reporting of external validation in included studies.

^dDowngraded ‐1 for risk of bias, due to major quality concerns in some studies related to the adequacy of assessment of the model’s uncertainty.

^eDowngraded ‐1 for risk of bias, due to major quality concerns in some studies related to the appropriateness of the model’s structural assumptions and the adequacy of assessment of the model’s uncertainty.

^fDowngraded ‐1 for indirectness, as travellers on evacuation flights comprised most of the studies; these are likely not representative of usual travels.