Providing expert opinion on issues relating to the Omicron variant, Professor Adam Cunningham, Professor of Functional Immunity at the University of Birmingham, said: “All the evidence points towards large numbers of people becoming infected with Omicron all across the globe.

“Because of this, there are additional concerns about Omicron that this is just the starting point for more variants to emerge, potentially maintaining its high levels of transmissibility but with maybe greater virulence.

Each new variant deriving from Omicron could challenge the efficiency of any cumulative, existing immunity to infection we have obtained from vaccines or previous infections, slowing down how quickly we can emerge from the pandemic.

“A worrying possibility is that the profile of the groups at greatest risk of infection changes. For instance, children are relatively spared from severe disease from the other variants.

“This can change and some reports suggest that Omicron can cause more severe disease in children, although this is far from certain. Early assessments suggest that antibodies induced after vaccination with the Pfizer vaccine give quite modest protection against infection.

“Most likely, because of T cells, there will be better protection by vaccines against the most serious presentations of Covid-19, but these are early days in our understanding of this. We do not know yet how the antibodies induced by the AstraZeneca vaccine will work, which is an area that needs addressing.

“Boosters most likely will enhance this protection, irrespective of whatever vaccine was given before, and really importantly, the benefit from boosting is likely to occur really quickly, within a few days of receiving the additional boost. It is likely that those who have been vaccinated and previously infected will have the best protection against Omicron, and it would be reasonable to think that a vaccine boost would help temper the spread and severity of infection with the Omicron variant.

“The appearance of new variants is not unexpected. What has been surprising has been the speed of appearance of Omicron and the sheer number of mutations observed in this virus.

“One possibility is that the variant emerged from an individual who was immunocompromised in one way or another and this individual acted as an incubator allowing the variant to develop over time. Another possibility, is that people with normal immune systems can maintain the virus for longer than we originally thought, or that it came from another source.

“If it did come from an immunocompromised patient then this would be especially concerning as it means such variants can emerge at multiple and near-random times in the future. That said, if infections with Omicron turn out to be less severe, and it’s a big if, then maybe evolving within an individual could help explain this.

“An additional point is that there are worrying reports that children may be more at risk of severe infection with Omicron, although this is far from certain. Whether true or not, it raises a bigger point that the longer the pandemic continues, the longer infections are maintained at high levels, aided by low levels of vaccination and use of other control measures, then the more likely that the groups at risk of severe disease may alter too.

“There are millions of new infections each month, which of course means we are more likely to see new variants emerging, each one challenging our ability to control these infections. Omicron shows why it is vital to vaccinate people, not just in the UK, but worldwide, as this virus does not respect borders.