A sub-variant of the highly contagious omicron coronavirus strain is even more infectious than the original version, according to a study conducted in Denmark.

The researchers examined the transmission of omicron sub-variant BA.2 versus BA.1 in 8,541 Danish households and 17,945 household members.

The yet-to-be peer-reviewed finding, posted on the preprint repository MedRxiv, indicates that the rapid spread of BA.2 could be related to an inherent increased transmissibility of the sub-variant.

There is also evidence to support immune evasive properties of the BA.2 sub-variant, the researchers said.

“The study found an overall secondary attack rate of 39 per cent in BA.2 infected households compared to 29 per cent in BA.1 infected households,” the researchers from Statens Serum Institut said.

“The risk of being infected was higher in unvaccinated persons compared with vaccinated and booster-vaccinated household members in both BA.2 and BA.1 infected households,” they said.

When comparing BA.2 relative to BA.1 infected households, there was an increased risk of infection in BA.2 infected households regardless of the vaccination status of the potential secondary case, indicating an inherent increased transmissibility of the BA.2 sub-variant, they said.