  Detections of mutations of the SARS-CoV-2 virus gave rise to new packages of
interventions. Among them, international travel restrictions have been one of
the fastest and most visible responses to limit the spread of the variants.
While inducing large economic losses, the epidemiological consequences of such
travel restrictions are highly uncertain. They may be poorly effective when the
new highly transmissible strain of the virus already circulates in many
regions. Assessing the effectiveness of travel bans is difficult given the
paucity of data on daily cross-border mobility and on existing variant
circulation. The question is topical and timely as the new omicron variant --
classified as a variant of concern by WHO -- has been detected in Southern
Africa, and perceived as (potentially) more contagious than previous strains.
In this study, we develop a multi-country compartmental model of the SIR type.
We use it to simulate the spread of a new variant across European countries,
and to assess the effectiveness of unilateral and multilateral travel bans.
