International travel restrictions may only be effective at controlling the spread of COVID-19 when applied in a targeted way, according to research published in The Lancet Public Health journal. The measures may have limited impact on the epidemic within individual countries except those with low levels of the virus or that have strong travel links with countries experiencing high rates of infection.
Every country in the world had imposed some form of travel restrictions – which have high economic and social costs – by late April 2020 as part of efforts to control the spread of the COVID-19. However, until now, no studies had produced global estimates of how the risk of importing cases relates to local transmission levels. Findings from this study could enable policymakers to determine where travel restrictions will have a major impact on slowing local transmission, and where they will have little effect.
Professor Mark Jit from the London School of Hygiene and Tropical Medicine, who led the study, said: "We recognise that these measures carry a high economic and social cost, so it is important that governments use travel restrictions in a targeted way. Before introducing restrictions, they should take into account local infection figures, epidemic growth rates, and the volume of travellers arriving from countries heavily-affected by the virus."
The findings indicate that international travel restrictions were most effective at limiting local transmission of the virus during earlier stages of the pandemic. This is because imported cases led to outbreaks in countries with very few – or no – existing cases.
The authors conclude that recommendations about international travel restrictions should not be applied uniformly. Countries must first consider local infection figures and epidemic growth rates, as well as the volume of travellers arriving from countries heavily-affected by COVID-19. For instance, in September 2020, the measures would be effective in New Zealand and China because the virus had been suppressed to such low levels in both countries that the expected number of imported cases is similar to the local rate, meaning arrivals could trigger a new local wave of infections.