New more infectious Covid-19 strain likely to be circulating in Ireland, says immunologist

Omicron XE is a combination of the existing variants of the Sars-CoV-2 virus

A more transmissible strain of the Omicron Covid-19 variant has been confirmed in Northern Ireland and is likely to be circulating in the State, an immunologist has said.

Trinity College Dublin professor of experimental immunology Kingston Mills said Omicron XE is a recombinant (combination) of the existing Omicron BA.1 and BA.2 strains. The UK has confirmed more than 1,200 cases of XE to date.

Just one case has been confirmed in the Republic while Northern Ireland's Public Health Agency announced on Monday there have been fewer than five cases to date.

Prof Mills suggested that the new strain could take over from BA.2 as the dominant strain in Ireland.


“In healthy people, it is not a severe disease but we have seen with Omicron that people are still ending up in hospital and in ICU. It is not a trivial disease for people who are older or vulnerable,” he explained.

Prof Mills said India is a big worry with six million cases so far this month alone with only about a third of the population vaccinated.

“It suggests it is a good environment for the emergence of variants. When you have a poorly vaccinated population with a vaccine that is not 100 per cent effective, that’s an environment that encourages the evolution of variants,” he said.

“The biggest worry is that new variants will emerge from India and transmit across the globe.”

There were 742 people with Covid-19 in Irish hospitals on Monday, a reduction of 12 on the previous day. This included 48 people in intensive care, an increase of three in 24 hours.

The last daily case number were published on Thursday when there were a total of 4,195 confirmed cases (1,936 PCR/2,259 antigen-tests).

The number of cases have dropped off in the Republic, but Prof Mills said there are still more than 4,000 cases a day translating to 30,000 a week. “There are so many people who have had it in the last two months that every workplace has been infected,” he suggested.

“The positive side is that a lot of people who have been infected are less likely to be re-infected. There is a lot of immunity in the population, but the people who have been cocooning though are very vulnerable.”

The World Health Organization (WHO) is continuing to monitor XE but has not yet deemed it a variant of concern or interest.

Its early estimates suggested XE had a growth rate of 10 per cent compared with BA.2, however the finding required “further confirmation”.

XE belongs to the Omicron variant until significant differences in transmission and disease characteristics, including severity, may be reported,” WHO said in its latest report.

"WHO continues to closely monitor and assess the public health risk associated with recombinant variants, alongside other Sars-CoV-2 variants, and will provide updates as further evidence becomes available." Deakin University chair in epidemiology Prof Catherine Bennett said

XE added “another layer” to the pandemic challenge but she was doubtful its emergence would change health authorities’ approach to living with the virus. “The ancestral strains of XE are two variants we know and, as they themselves are quite closely related, it is less likely to lead to a step change in risk for us, or for the effectiveness of our existing acquired immunity from vaccination and infection,” she said.

“So far there is some evidence XE might be a bit more infectious again, but no change has been shown in relation to severity of illness which was also quite similar between B.A.1 and B.A.2. XE sequences had been reported internationally and it was too early to tell if the variant would become dominant and circulate widely.

“But they said continued emergence of further Sars-CoV-2 lineages and recombinant variants was likely as the virus continued to mutate.”

Ronan McGreevy

Ronan McGreevy

Ronan McGreevy is a news reporter with The Irish Times