Evidence on the Effectiveness of Covid-19 International Travel Measures
Evidence on the effectiveness of travel measures to prevent or slow the spread of Covid-19 and guidance on how and when to apply these measures is limited and the results are mixed. Given the social and economic disruptions that these measures can have, and their potential adverse effects on preventing the spread of the disease, WHO among others have cautioned implementing measures that are not supported by robust evidence. The scope of the search for this report was broad, covering all reported international travel restrictions to contain or slow the spread of Covid-19 and without geographical limitations. The results are therefore more general than restriction- or country-specific and more targeted studies may be omitted from the search due to these wide search parameters. There is general agreement across the literature that some form of travel restriction in the early stages of a disease or variant spread can lead to a slowing of the rate of infections in countries yet to be affected. The majority of studies conducted on travel restrictions adopt a modelling approach, and a systematic review conducted in December 2020 concluded that the quality of observational studies was low to very low (Bou-Karroum et al., 2021). Determining the specific effects of different travel measures is difficult as many studies examine the effects of combined measures. Few studies separate different types of restrictions and much of the modelling on international transmission rates uses data on the movements of people as a proxy for travel restrictions, therefore limiting the ability to observe how measures were implemented except for the timing of measures at different points in the pandemic. Limited country-level evidence was identified for this report and few global studies examine contextual factors that might affect the effectiveness of travel restriction measures. A targeted search for evidence on the effects of travel restrictions on different variants of Covid-19 did not reveal any studies making this distinction.