An infectious diseases expert has said it is too early to know whether the growing prevalence of a sub-variant of the Covid-19 Omicron variant will be a further “game changer” in the pandemic.

The BA.2 sub-lineage of Omicron is expected to become the dominant strain in the State by the end of the month, with early research suggesting it may be more transmissible and could cause more severe disease.

Prof Sam McConkey said he was "cautiously optimistic" about the sub-variant and that he was "hopeful" the severity of the disease it causes would be broadly similar to Omicron. He said one important factor to watch would be the level of "cross immunity" previous Omicron infection offered against the sub-variant.

Hospital Report

Dr Michael Power, Health Service Executive clinical lead for intensive care and a consultant in Beaumont Hospital, Dublin, said the spread of the sub-variant had not yet had any noticeable impact on the numbers in ICU with Covid-19.

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“We haven’t seen any signal in the ICU system in terms of admissions and in terms of severity,” he said, adding that health officials were “keeping a very close eye” on it.

Prof Kingston Mills, immunologist at Trinity College Dublin, said a laboratory study in Japan examining BA.2 suggested it might be more severe than Omicron. This would be "not great" if it turned out to be the case, he said.

Similarly, there were indications that people who had been infected with Omicron might not have as much immunity against reinfection from the sub-variant. “There’s quite a lot of difference in the sequence of this variant,” he said.

He cautioned against any rush to “scaremonger” over the strain as there was a lack of “real-world data” about its nature, and whether it was more severe. He said it was “very encouraging” to see UK data suggest the efficacy of Covid-19 vaccines against BA.2 was similar to their performance against the original Omicron variant, particularly among those who had received booster shots.

One senior HSE source said developments around the sub-variant were being kept under close watch, as was standard with any emerging variants of interest and potential concern.

Chief medical officer Dr Tony Holohan recently told the Government that about 40 per cent of new Covid-19 cases were likely to be from the BA.2 sub-variant. In a letter to Minister for Health Stephen Donnelly, he said the sub-lineage of Omicron was growing by almost 10 per cent a day, and was expected to be dominant by the end of the month.

The spread of the sub-variant comes as the Government prepares to accept public health advice to end compulsory mask-wearing in almost all settings from February 28th, with the National Public Health Emergency Team to also be wound down.

The Department of Health did not publish Covid-19 case data at the weekend but the number of people being treated for the disease in Irish hospitals increased by 15 on Sunday to 594. This included 52 people in intensive care, a reduction of three in 24 hours.

An online booking system for Covid-19 vaccines for children aged five-11 opened on Sunday. The HSE system aims to allow people to arrange appointments for their child at a “time that suits them”, said Dr Lucy Jessop, director of public health at the National Immunisation Office.

Children in this age group will be vaccinated in separate clinics to those aged 12 or over and will receive a different dose to those given to older children and adults. The Pfizer Covid-19 vaccine was approved for use in children in this age group by the European Medicines Agency (EMA) in November.