The World Health Organization has designated the risk from the omicron variant of COVID-19 as “very high” but maintains there is “considerable uncertainty” around this classification.

The health arm of the United Nations said in a technical brief for member states on Sunday that the variant’s mutations could make it likelier to transmit despite precautions. It also said that “preliminary evidence suggests there may be an increased risk of reinfection” and that “the likelihood of potential further spread of Omicron at the global level is high.”