Two more cases of a new Covid-19 variant of concern have been detected in Ireland, as more extra-transmissible strains of the Omicron variant gain a foothold here.
Four cases of BA.4, a sublineage of Omicron, 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 as yet been identified here, he says in his latest weekly report on the pandemic.
In addition, 23 cases of another Omicron variety, 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 US and is being blamed for a new wave of cases there.
In the US, Dr Holohan noted, cases have risen 33 per cent week-on-week and hospital admissions are up 19 per cent.
BA.2.12.1 has been estimated to be about 25 per cent more transmissible than the BA.2 subvariant of Omicron, which is dominant in Ireland. BA.2 was 50 per cent more transmissible than the original Omicron variant and drove a surge in cases as it spread here in the spring.
BA.4 and BA.5 were designated variants of concern by the European Centre for Disease Control earlier this month. They were first identified in South Africa in January and February this year, and have gone on to become dominant there.
By mid-May, BA.4 and BA.5 accounted for for 89 per cent and 7 per cent of cases sequenced in South Africa, which has experienced a moderate increase in Covid-19 hospitalisations. 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 the two strains have a growth advantage most likely because they can evade immunity provided by prior infection and vaccination, particularly as this wanes over time.
Scientists expect BA.4 and BA.5 will eventually replace the BA.2 sublineage that is dominant at present.
However, there is no indication they are any more severe than previous Omicron lineages. The ECDC has warned they may cause increased virus transmission in Europe in the near future.
Dr Holohan, in his May 20th report, says the overall epidemiological situation in Ireland remains broadly positive “albeit we will need to continue to monitor developments with emerging variants over the coming weeks”.
“Although there continues to be high levels of infection and a significant number of cases receiving general hospital care, the numbers of detected infections and hospitalised cases have reduced considerably over recent weeks.” ICU numbers are also down.
The hospital system remains under considerable pressure, he notes, with few available beds and with Covid-19 continuing to impact on acute capacity and operational effectiveness in some locations.
Dr Holohan says a significant proportion of younger people have not taken a booster vaccine against Covid-19; 37 per cent of 35-44 year-olds, 43 per cent of 25-34 year-olds and 52 per cent of 16-24 year-olds have not received a first booster.
Meanwhile, over 70 per cent of those aged over 65 have yet to get a second booster.
“It is important that these eligible groups continue to be encouraged to avail of booster vaccination in order to confer optimal protection against the risk of severe disease, as well as against other potential long-term consequences of infection,” he says.