Two new subvariants of Omicron - BA.4 and BA.5 - are spreading much faster than other corovanirus variants in Europe, which could lead to more hospitalisations
and deaths as they become dominant, the EU's disease prevention agency said on Monday (June 13).
Most EU countries have so far detected low rates of the two subgroups. But in countries where the proportion has risen - such as Portugal, where BA.5 accounted for
87 per cent of cases by May 30 - there have been surges in overall cases, according to the European Centre for Disease Prevention and Control (ECDC).
The two sublineages were added to the World Health Organization's monitoring list in March and have also been designated as variants of concern by the ECDC.
Variants BA.4 and BA.5 do not appear to carry a higher risk of severe disease than other forms of Omicron.But an increase in case numbers from higher transmission
rates risks leading to an increase in hospitalisations and deaths, the agency said.
"The growth advantage reported for BA.4 and BA.5 suggest that these variants will become dominant," ECDC said in a statement on its website.
The World Health Organization says it is tracking a few dozen cases of two new sub-variants of the highly transmissible Omicron strain of the coronavirus to assess whether they are more infectious or dangerous.
It has added BA.4 and BA.5, sister variants of the original BA.1 Omicron variant, to its list for monitoring. It is already tracking BA.1 and BA.2 - now globally dominant - as well as BA.1.1 and BA.3.
The WHO said on Monday (April 11) it had begun tracking them because of their "additional mutations that need to be further studied to understand their impact on
immune escape potential".
Viruses mutate all the time but only some mutations affect their ability to spread or evade prior immunity from vaccination or infection, or the severity of disease they cause.
For instance, BA.2 now represents nearly 94% of all sequenced cases and is more transmissible than its siblings, but the evidence so far suggests it is no more likely to cause severe disease.
Britain has become the first country to approve a Codiv-19 vaccine that targets both the original and Omicron variant of the virus.
Medicines regulator MHRA approved the so-called bivalent vaccine made by US drug company Moderna as a booster for adults.
The agency's decision was based on clinical trial data that showed the booster triggered "a strong immune response" against both Omicron (BA.1) and the original
2020 virus, it said.
The MHRA also cited an exploratory analysis in which the shot was also found to generate a good immune response against the currently dominant Omicron offshoots BA.4
and BA.5.
"The first generation of Covid-19 vaccines being used in the UK continue to provide important protection against the disease and save lives," MHRA chief executive
June Raine said in a statement.
"What this bivalent vaccine gives us is a sharpened tool in our armoury to help protect us against this disease as the virus continues to evolve."