Omicron is spreading rapidly throughout the world, with experts claiming that 40% of the global population will be infected within the next two months. This sounds quite startling, but we still don’t really know whether omicron causes more severe disease than other variants of concern. The signs so far are good, though. With the previous widespread variant, delta, there was a clear link from infection to hospitalisation and then, in some patients, ICU admission and death. This doesn’t seem to be as apparent with omicron. However, the director general of the World Health Organization, Tedros Ghebreyesus, said on January 6: “While omicron does appear to be less severe compared to delta, especially in those vaccinated, it does not mean it should be categorised as mild.” The question is why might it be less severe than delta? Are there changes in omicron that make it less troublesome? There are two aspects …