In late November, scientists in South Africa and Botswana identified a new variant of the virus that causes Covid. This variant — later named Omicron — was spreading rapidly throughout South Africa, particularly in Gauteng, its most populous province. As well as reporting these concerning epidemiological facts, South African scientists worked quickly to identify Omicron’s genetic sequence and to alert the world with further bad news: Omicron has a large number of mutations in the region of the virus that our immune system recognises after we are vaccinated.