Two more cases of a worrying new variant of Covid-19 have been detected in Ireland, as more extra-transmissible strains of the Omicron variant gain a foothold here.
Four cases of BA.4, an Omicron subline, have been detected, up from two a week earlier, according to chief medical officer Dr Tony Holohan.
No cases of a related variant, BA.5, have yet been identified here, it says in its latest weekly pandemic report.
Additionally, 23 cases of another variety of Omicron, BA.2.12.1, have been detected in Ireland, according to Dr Holohan. BA.2.12.1 currently accounts for half of all cases in the United States and is responsible for a new wave of cases there.
In the United States, Dr. Holohan noted, cases were up 33% week over week and hospital admissions were up 19%.
BA.2.12.1 is estimated to be around 25% more transmissible than Omicron’s BA.2 sub-variant, which is dominant in Ireland. BA.2 was 50% more transmissible than the original Omicron variant and led to an increase in cases as it spread here in the spring.
BA.4 and BA.5 were designated variants of concern by the European Center for Disease Control earlier this month. They were first identified in South Africa in January and February this year, and have become dominant there.
In mid-May, BA.4 and BA.5 accounted for 89% and 7% of sequenced cases in South Africa, which has seen a moderate increase in Covid-19 hospitalizations. In Portugal, BA.5 now accounts for two-thirds of cases. In the UK, 115 cases of BA.4 and 80 cases of BA.5 have been detected.
Dr. Holohan says both strains have a growth advantage most likely because they can evade the immunity provided by previous infection and vaccination, especially as this wanes over time.
Scientists expect BA.4 and BA.5 to eventually replace the BA.2 sublineage which is currently dominant.
However, there is no indication that they are more severe than previous Omicron lines. The ECDC has warned that they could lead to increased transmission of the virus in Europe in the near future.
Dr Holohan, in his May 20 report, says the overall epidemiological situation in Ireland remains broadly positive “although we will need to continue to monitor the development of emerging variants over the coming weeks”.
“While there continue to be high levels of infection and a significant number of cases receiving general hospital care, the number of infections detected and cases hospitalized has decreased significantly over the past few weeks.” Intensive care numbers are also down.
The hospital system remains under considerable pressure, he notes, with few beds available and with Covid-19 continuing to impact acute capacity and operational efficiency in some locations.
Dr Holohan says a significant proportion of young people have not taken a booster shot against Covid-19; 37% of 35-44 year olds, 43% of 25-34 year olds and 52% of 16-24 year olds did not receive a first reminder.
Meanwhile, more than 70% of people over the age of 65 have yet to receive a second booster.
“It is important that these eligible groups continue to be encouraged to receive booster vaccination to confer optimal protection against the risk of severe disease, as well as against other potential long-term consequences of infection,” he said.