Following an update on the omicron variant situation in the UK from Sajid Javid in the House of Commons on Monday, here is a general comment from Professor Francois Balloux.
Prof Francois Balloux, Professor of Computational Systems Biology and Director, UCL Genetics Institute, UCL, said:
“The number of cases of the omicron variant have been rising fast in the UK over recent days. Though, at this stage, Omicron represents only a small fraction of all Covid-19 cases in the UK, with the delta variant still causing the bulk of cases (~99%).
“This situation is likely to change in the near future with the number of omicron cases doubling roughly every three to days. If this rate of increase were maintained, omicron would be expected to become the most widespread variant in the UK within a month or so.
“Omicron seems to be more transmissible primarily because it is more likely to (re-)infect people who have acquired immunity through prior infection and/or vaccination. Though those ‘breakthrough infection’ are not necessarily associated to severe symptoms.
“The rapid spread of omicron in many countries around the world might also be fuelled by a shorter incubation period, though, this will need to be confirmed by future studies on ‘transmission chains’ (i.e. reconstructions of “who infected whom”).
“Early, largely anecdotal evidence suggests omicron may be less virulent than delta. This would be good news if confirmed, in principle.
“It remains that even if omicron infections were associated to fewer hospitalisations and deaths, a small fraction of severe outcomes out of a very large number of infections could still cause intense pressure on healthcare systems.
“Also, if it were to be confirmed that omicron causes on average less severe symptoms than delta, its current frequency in the UK may be underestimated, as people infected with omicron may be less likely to come forward to get tested.
“Given the already widespread circulation of omicron in the community in the UK, travel bans are unlikely to contribute much to a reduction of the number of cases in the UK at this stage.
“Travel bans can be most effective when enforced in the early stages of an epidemic, and in places where case numbers remain low. Once introduction from abroad represents only a minute fraction of locally acquired cases, travel bans stop being particularly effective at reducing the number of infections locally.”
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