IF THERE is one lesson the covid-19 pandemic has taught the world, it is that acting early pays off. Wait a week for better data on which to base a decision and you can find yourself down a path of no return, with cases rising steeply. So 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”.
The concerns with Omicron are indeed many. The biggest is that it may have the ability to spread more easily than Delta, the variant that dominates cases of covid around the world today. If so, Omicron could supplant Delta within months. In that case, Omicron would cause bigger outbreaks that flare up faster than Delta and are harder to stop. Another worry is that today’s vaccines and drugs against covid 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. In the meantime many countries are trying to stop the new variant from arriving on their shores inside travellers—and rightly so. They are buying time to prepare for the worst while hoping for the best.
The first signs that a new variant may be spreading emerged in South Africa earlier this week, when covid infections increased suddenly and sharply, from fewer than 300 cases on November 16th to more than 1,200 on November 25th. The vast majority of these infections were in one province, Gauteng, which has Johannesburg as its capital.
Further analysis confirmed that the new variant was spreading fast in many other provinces in South Africa, even though the numbers were still small. This pattern suggests that Omicron may be outcompeting Delta. The nature of Omicron’s mutations adds backing for this hypothesis. It has about 50 of them, 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.
At first it seemed as if the infections were linked to one big superspreading event, such as a student party. That would be the sort of outbreak in which a new variant erupts briefly and then dies away. But new cases in Gauteng instead became more dispersed over time. That prompted South African scientists to look at the genomic sequence of viral samples, which is how they spotted the new variant.
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). Various combinations of Omicron’s mutations are present in all of the variants of concern to have emerged so far.
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 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, but they could defeat some antibody therapies, which are given to people unable to mount an immune response.
All in all, lots about Omicron remains to be discovered. What is clear, however, is that the world is better placed to resist it than when Delta emerged in India at the end of last year. By the time Delta had been identified as a variant of concern, it had already spread to many parts of the world, eventually seeding wave after wave of the pandemic. It remains to be seen whether Omicron poses a global threat on such a scale.
Even if Omicron comes to dominate in South Africa, it is unclear that it will displace Delta in other parts of the world. South Africa had a wave of the Beta variant that did not become established elsewhere. Likewise, Alpha, which swept across Europe, never became established in South Africa. These patterns may have to do with variations in demography and with common infections that interact with SARS-CoV-2 in poorly understood ways.