Irish authorities said that cases of the BA.4 variant were detected earlier this month and identified after whole-genome sequencing of a sample of confirmed cases on May 7.
BA.4 is a new sub-strand of the highly contagious Omicron coronavirus strain.
Analysis of available data by the UK Health Security Agency (UKHSA) suggests that BA.4 and BA.5, another variant of concern currently spreading, are expected to have a “growth advantage” over Omicron BA.2, which is now the dominant variant.
The European Centre for Disease Prevention and Control has labelled the two new strands as variants of interest while the UK has labelled them variants of concern.
As of May 20, the UK had recorded 115 cases of probable or confirmed BA.4, with 67 in England, 41 in Scotland, six in Wales and one in Northern Ireland.
A further 80 cases of BA.5 were identified, with 48 in England, 25 in Scotland, six in Northern Ireland and one in Wales.
“Whilst the impact of these variants is uncertain, the variant classification system aims to identify potential risk as early as possible,” said Dr Meera Chand, UKHSA director of clinical and emerging infections.
However, initial findings suggest BA.4 and BA.5 have a degree of “immune escape” — meaning the immune system can no longer recognise or fight a virus — which is expected to contribute to their growth advantage over BA.2, the UKHSA said.
The European Centre for Disease Prevention and Control said the variants could lead to a significant rise in cases of Covid-19 in the EU in the coming weeks and months.
While there is no indication that it is more severe, it could evade protections provided by vaccines and or past infection.
Dr Tony Holohan, chief medical officer to Ireland's health minister, said that while authorities will continue to monitor developments with emerging variants in the coming weeks, the situation in the country had a “broadly positive outlook”, RTE reported.