But there is no clear sign that BA.2 is substantially different from the original Omicron strain, authorities say.

WHO says there so far is 'no indication that there is a change in severity' in the BA.2 sub-variant.

Researchers say those who have been fully jabbed, particularly those who have received a booster dose, are much less likely to catch the strain.

The BA.1 lineage currently accounts for 98% of all cases globally but in Denmark has been pushed aside by BA.2, which became the dominant strain in the second week of January.