A 2014 review of scientific evidence conducted by a group of British researchers from Public Health England and the University of Nottingham concluded that travel bans can work but only for stalling the arrival of a pandemic influenza virus into a country. To effectively delay virus importation, a ban must shut down almost all travel into a country, the study found. But according to the researchers, even these drastic restrictions may have limited utility if the virus involved is moderately to highly infectious — which is the case with SARS-CoV-2 and its variants.

During the current pandemic, it is true that countries such as New Zealand and Australia have used travel bans to reduce importation of SARS-CoV-2. But their bans have been near-total, early, and paired with effective contact tracing and quarantine systems. Similarly, many small island nations such as the Polynesian country of Tuvalu — population approximately 12,000 — have kept the coronavirus out after severely restricting travel.

So, yes: Travel bans can work under limited conditions. But the Omicron-related southern Africa travel ban imposed by the United States is too selective, focuses on many countries where the variant hasn’t been documented and excludes many more where the variant has been detected.