THE FIRST CASES of a new Covid variant of concern have been detected in Ireland.

The European Centre for Disease Control earlier this month labelled BA.4 and BA.5 as variants of concern, with chief medical officer Dr Tony Holohan confirming that two cases of BA.4 were identified in Ireland earlier this month.

What are these variants, what do we know about them, and what type of impact could they have?
BA.4 and BA.5 are sublineages of Omicron (as is BA.2, currently dominant in Ireland and what caused our most recent post-Christmas wave of infection). This means they are not genetically distinct enough from Omicron to be classed as a different variant such as Delta or Alpha, but contain some genetic mutations.

There are many, many more sublineages of Omicron, most of which cause little or no concern, but BA.4 and BA.5 have stood out to scientists. They first emerged in January and February of this year.

The sublineages are believed to be responsible for a renewed wave of infection in South Africa which started in early May. The data currently indicates that this is less severe than its previous record-breaking Omicron wave, and there are even signs it is slowing.

The sublineages have now started to picked up more frequently in Europe, where they account for an increasing proportion of cases in countries like Austria, Germany, and – where it is now dominant – Portugal.

Why is it spreading?

It takes time to learn about new variants, but what’s currently apparent is that BA.4 and BA.5 have the potential to cause another wave of infection through immune escape.

These sublineages are sufficiently different from previous Omicron sublineages that our immune system might not be able to recognise them as well if you’ve already been infected with Omicron – but not anywhere to same extent as when a truly ‘new’ variant previously arrived on the scene, like Alpha, Delta, or BA.1 Omicron.

There is also the basic fact that immunity from previous Omicron waves is starting to wane.

If you haven’t been infected with Omicron, you remain just as susceptible to a breakthrough infection from these sublineages, regardless of which one we’re dealing with.

If you are fully vaccinated and boosted, you will still have strong protection against severe illness.

There is currently no evidence that BA.4 and BA.5 cause more severe illness than previous Omicron sublineages (that data takes time to gather), although it still has the potential to be a debilitating and potentially fatal illness.

There is some evidence to suggest that not only is there an increased chance of immune escape, but the sublineages are also more transmissible.

What does this mean for Ireland?

While just two cases of BA.4 have been detected, Ireland is fully analysing few individual cases to determine with variant is responsible, so it is highly likely it is responsible for more cases than is currently apparent.

If BA.4 and BA.5 have an advantage over BA.2, which by all accounts they appear to, one will eventually become the dominant variant in Ireland, especially when a significant number of protections against the spread of Covid-19 have been removed or made voluntary in Ireland.

Speaking more generally about Europe, the ECDC said the variants “could cause a significant overall increase in Covid-19 cases in the EU/EEA in the coming weeks and months”.

As in previous waves, if Covid-19 case numbers increase substantially, some level of increased hospital and ICU admissions is likely to follow.

How Ireland could fare isn’t yet clear – the ECDC’s warning is clear, that an uptick in infections can be expected.

While some Omicron immunity is waning, there are a lot more people with some level of protection against the variant than when it first arrived in Ireland.

Many people more at risk of severe illness have also received another booster since then. Another factor is that South Africa and Portugal didn’t have as pronounced a BA.2 wave as Ireland did, and BA.2 is more similar to the new variants of concern than BA.1.

Hospitals could remain better protected, and there is no suggestion of new restrictions, but wider societal disruption similar to what was experienced during the BA.2 wave remains a possibility.