Experts say the new variants could cause "a significant overall increase in Covid cases in the EU".
Two cases of a new
Covid variant that has the potential to become the dominant strain have been detected in Ireland.
The BA.4 variant was confirmed to be present in the country on Sunday (22 May).
BA.4 is a sub-lineage of Omicron, which is currently the most dominant strain in Ireland.
The European Centre for Disease Prevention and Control (
ECDC) reclassified both BA.4 and another variant, BA.5, from "variants of interest to variants of concern".
The variants were first discovered in South Africa in January 2022 and February 2022 respectively, and have since become the dominant variants there.
Cases of BA.5 have shot up in Portugal, accounting for 37% of all positive Covid cases as of 8 May.
BA.5 is expected to become the dominant strain in Portugal this week.
"The currently observed growth advantage for BA.4 and BA.5 is likely due to their ability to evade immune protection induced by prior infection and/or vaccination, particularly if this has waned over time," said the ECDC.
Those who are unvaccinated are currently unlikely to be protected against symptomatic infection with BA.4 or BA.5, even if they have had a prior infection of BA.1.
There is currently no sign that the BA.4/BA.5 variants are any more severe compared to previous Omicron lineages.
"Taken together, this indicates that the presence of these variants could cause a significant overall increase in Covid cases in the EU/EEA in the coming weeks and months," the ECDC warned.
"The overall proportion of BA.4 and BA.5 in the EU/EEA is currently low but the high growth advantages reported suggest that these variants will become dominant in the EU/EEA in the coming months.
"Based on the limited data currently available, no significant increase in infection severity compared to the circulating lineages BA.1 and BA.2 is expected.
"However, as in previous waves, if Covid-19 case numbers increase substantially, some level of increased hospital and ICU admissions is likely to follow."
