Omicron BA.4 and BA.5 are likely to have a “growth advantage” over the current dominant variant, Omicron BA.2, data by the UK Health Security Agency (UKHSA) suggests.
However, only a small number of these two types of variant have been identified so far in the country.
As of May 20, 115 cases of probable or confirmed BA.4 have been identified, with 67 in England, 41 in Scotland, six in Wales and one in Northern Ireland.
Some 80 cases of BA.5 have been identified, with 48 in England, 25 in Scotland, six in Northern Ireland and one in Wales.
Dr Meera Chand, UKHSA director of clinical and emerging infections, said: “The reclassification of these variants as variants of concern reflects emerging evidence on the growth of BA.4 and BA.5 internationally and in the UK.
“Whilst the impact of these variants is uncertain, the variant classification system aims to identify potential risk as early as possible.
“UKHSA is undertaking further detailed studies. Data and analysis will be released in due course through our regular surveillance reporting.”
There is currently no data to determine the impact of the variants on hospital admissions in the UK.
But initial findings suggest BA.4 and BA.5 have a degree of “immune escape” – meaning the immune system can no longer recognise or fight a virus – which is likely to contribute to their growth advantage over BA.2, the UKHSA added.