Podcast: Can international travel-related control measures contain the spread of the COVID-19 pandemic?

Cochrane has already produced many rapid reviews to help decision makers with their response to the COVID-19 pandemic and we are updating these to try to keep up with the accumulating evidence. In this podcast, lead author, Jake Burns from the University of Munich in Germany describes the latest findings of our review of the effects of control measures for international travel, which was updated in March 2021.

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Monaz: Hello, I'm Monaz Mehta, editor in the Cochrane Editorial and Methods department. Cochrane has already produced many rapid reviews to help decision makers with their response to the COVID-19 pandemic and we are updating these to try to keep up with the accumulating evidence. In this podcast, lead author, Jake Burns from the University of Munich in Germany describes the latest findings of our review of the effects of control measures for international travel, which was updated in March 2021.

Jake: Travel-related control measures, even as they've been implemented during the COVID-19 pandemic, can refer to many things, but in the latest version of our review we focused specifically on restrictions that reduce cross-border international travel. These include measures such as border closures or restricting entry for people from high-risk countries, screening of travelers at borders by asking about symptoms, measuring temperature or testing for the virus, quarantining travelers, and sometimes combined measures. We were interested in whether these measures led to cases of COVID-19 being avoided or a shift in the development of the epidemic. We also wanted to know how many cases of COVID-19 were detected because of each control measure.
We completed the first version of this review in September 2020 and have now expanded it to include 62 studies of the impact of international travel-related control measures; with most of these, 49, being modelling studies, while 13 were observational studies.
The evidence base has expanded considerably since our original review: we identified studies from a larger geographical spread, studies from later stages of the pandemic, and more so called 'real-world' studies. Given the broad range of measures assessed and differences in study design and analysis methods, it remains challenging to draw general conclusions about the effectiveness of the measures but we did observe some trends. 
Most studies observed that travel restrictions reducing cross-border travel, like the closure of borders and restricting travelers from high-risk countries, are likely to be beneficial. However, the size of this effect varied widely across studies. All studies showed that screening at borders, whether based on checking for symptoms or testing, will likely show some benefit over no measures; but they also showed that these measures are likely to miss a meaningful proportion of cases. Quarantining returning travelers was observed to be beneficial across studies, although the size of the effect ranged widely. Lastly, combinations of screening at borders and quarantine were generally observed to be more impactful than the individual measures themselves. Importantly, many studies suggest that observed effects might vary widely depending on factors such as levels of community transmission, travel volumes and duration, other public health measures in place, and the exact specification and timing of the measure.
Despite the promising findings in this update, there are some important caveats to keep in mind. Although we identified an expanded and improved evidence base, the certainty of the evidence remains quite low. This means that although some of the studies were quite well conducted, our confidence in the overall results is limited. So, although some evidence does exist to help support decision makers, there are still important questions that need to be answered. Future research should aim to improve the evidence base by focusing on rigorous evaluation methods as well as focusing in on other factors that influence the effectiveness of the measures.

Monaz: If you would like to read the full review and watch for further updates as new evidence becomes available, it's available free online. Just visit Cochrane Library dot com and search 'international travel and COVID-19'.

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