While more than 50 countries have stepped up border controls in the wake of the Omicron variant of coronavirus, but scientists say travel restrictions have come too late and could even slow studies of the new super mutant.
The team of scientists said restrictions -- especially those targeting only travellers from a handful of countries -- are unlikely to keep Omicron out, and come at significant cost to the countries concerned, Nature reported.
The travel bans also risk slowing down urgent research on Omicron, by limiting the arrival of imported lab supplies.
"I'm not that optimistic that the way in which these measures are being rolled out right now will have an impact," Karen Grepin, a health economist at the University of Hong Kong, was quoted as saying.
"It's too late. The variant is circulating globally," added Kelley Lee, who studies global health at Simon Fraser University in Burnaby, Canada.
Most travel bans target South Africa, which raised the alarm about Omicron on 24 November, and Botswana, which also reported early cases.
Many nations are also banning visitors from neighbouring Lesotho, Eswatini, Zimbabwe, and Namibia.
Researchers said border restrictions might deter nations from alerting the world to future variants. They will also slow down urgent research, because few planes carrying cargo -- including lab supplies needed for sequencing -- are now arriving in South Africa, the report said.
Several researchers are racing to understand how Omicron's transmissibility and ability to evade immunity created by vaccines differ from those of pre-existing variants of SARS CoV-2. They're also investigating the relative severity of the illness Omicron causes.
"The travel ban will paradoxically affect the speed at which scientists are able to investigate," Shabir Madhi, from the University of the Witwatersrand in Johannesburg, South Africa, was quoted as saying.
While restrictions are most effective when they are implemented rapidly, the Omicron-related border closures were too late, Grepin said, as researchers might also struggle to share samples with global collaborators, the report said.
The variant has now been detected in nearly 38 countries, including India, US, the Netherlands, the UK, Australia, and Japan. Some nations acquired the infection even before South Africa reported the variant to the WHO. "As soon as countries start looking for it, they're finding it, so the advantage of time is probably gone," Grepin said.
Restrictions are also probably most effective at slowing the number of initial cases in a country when they reduce the total volume of international arrivals, rather than when they pick and choose specific countries, the researchers said.
Border-control measures should be used alongside efforts to strengthen public-health interventions such as social distancing, mask wearing and vaccination, said Grepin, because genomic studies have shown that cases will eventually slip through.
