Researchers have been closely observing a new variant, BA.2 which is a subvariant of Omicron. This new strain's growth has been especially rapid, with Danish scientists at the Statens Serum Institut saying it is 1.5 times more transmissible than the original Omicron variant, BA.1.

They are quite similar, sharing 32 mutations but differ by 28. The difference between BA.1 and BA.2 is greater than the original variant and the Alpha variant. These kinds of differences can lead to different properties which concern infectiousness, vaccine efficacy or severity – although there is currently no data on the severity of BA.2.

The UKHSA has said that the new variant has an increased growth rate compared to the BA.1, the Omicron variant. Its contact tracing data illustrates that transmission is likely to be higher compared to those for contacts of other Omicron cases.

Dr Susan Hopkins, Chief Medical Advisor for UKHSA has said: “We now know that BA.2 has an increased growth rate which can be seen in all regions in England. We have also learnt that BA.2 has a slightly higher secondary attack rate than BA.1 in households.”

“Although hospitalisations and deaths remain low, cases are still high in some areas and some age groups so it’s important that we continue to act cautiously as restrictions are lifted.”

Almost 50% of US states have reported the presence of BA.2. Worldwide, 40 countries have uploaded just over 8,000 BA.2 sequences to GISAID (a global science initiative that provides open access to genomic data of COVID-19) since 17 November 2021, over 6,000 of these from Denmark, where BA.2 now accounts for almost half of all Danish Omicron variant cases.

When BA.2 was first detected in November last year in South Africa, scientists worried that it was going to be more problematic to track than BA.1. The original Omicron variant has a specific mutation, a deletion in the spike gene, that appears on PCR tests, which makes it easy to discern Omicron cases. However, BA.2 does not have this mutation, leading to many potentially misleadingly nicknaming the strain a ‘stealth’ variant.

While BA.2 may not look like the original strain of Omicron, this does not mean it is undetectable and positive cases will still appear as positive on a test. The only concern is that it may not look like BA.1 on the test.

Cornelius Rommer, a scientist at the University of Basel, Switzerland tweeted:

The UKHSA has currently labelled the variant as a ‘variant under investigation’. Currently, the original Omicron variant is dominant in the UK, and the percentage of BA.2 cases is low.

Meanwhile, to stay safe, we can make sure we get our booster vaccines and where necessary, wear a mask and social distance.