When news emerged on November 25th in South Africa of a worrying new variant of the SARS-CoV-2 virus, many countries in Europe and elsewhere banned travel from countries in southern Africa within a day. On November 26th the World Health Organisation named the variant Omicron, a Greek-alphabet designation which, as a rule, it reserves only for “variants of concern”. There is a fear that today’s vaccines and drugs against COVID-19 may be less potent against Omicron and may therefore need to be redesigned. At the moment, these are only fears based on hints drawn from early data on Omicron emerging from South Africa. Whether these fears will come to pass is far from certain. It will take weeks or even months before there is solid evidence from laboratory and other studies on how much of a threat Omicron really poses. Omicron has about 50 mutations, an exceptionally large number. Most worrying are ten found in the receptor-binding domain (RBD) of the virus’s spike protein. The RBD is the part of the virus that attaches to human cells, enabling the virus to enter and infect them. By comparison, the Beta variant has three changes to the RBD and Delta only two. With mutations, quantity is not necessarily quality. But several of those in Omicron have been found in studies of other variants to make the virus more infectious. Some of them make it easier for SARS-CoV-2 to evade the body’s innate immune response (the immune system’s first reaction), others weaken its antibody response (a defence mechanism built as a result of prior infection or vaccination). If the mutations in Omicron turn out to make covid vaccines less potent, the jabs may have to be tweaked. On November 26th Pfizer and BioNTech, makers of the COVID-19 jab that is most widely used in Western countries, said that they would be able to rework their mRNA vaccine within six weeks and ship the first batches within 100 days. The mutations in Omicron do not appear to be a threat to the efficacy of antiviral medicines for COVID-19 but they could defeat some antibody therapies, which are given to people unable to mount an immune response. Read more here: https://www.economist.com/science-and-technology/2021/11/26/a-new-covid-19-variant-has-emerged.