Two types of Omicron classified as Covid variants of concern in UK

Small number of BA.4 and BA.5 cases identified but data suggests ‘growth advantage’ over dominant BA.2

Two types of the Omicron known as BA.4 and BA.5 have been labelled as variants of concern in the UK after new evidence on their growth, officials have revealed.

The wave of Omicron that hit the UK over the winter involved a form of the virus known as BA.1, with the sub-lineage BA.2 driving a subsequent wave in spring 2022.