Everything you need to know about the BA.2 COVID subvariant

Or rather, a subvariant.

BA.2 is not so different from Omicron (BA.1) that it justifies a new Greek letter, but it is different. It has already appeared in a string of countries, including Denmark, India, the UK, the US, the Philippines, Norway, Sweden and, now, Australia.

The World Health Organisation calls it an "Omicron variant of concern" which "is currently the dominant variant circulating globally".

A study done in Denmark, where the subvariant has become the dominant type of coronavirus, suggests it is more transmissible than the original Omicron, for vaccinated and unvaccinated people alike.

But the WHO says this difference is a matter of degree. Omicron was much more transmissible than Delta but the difference between the variants of Omicron was not such a big step-change.

"This difference in transmissibility appears to be much smaller than, for example, the difference between BA.1 and Delta. Further, although BA.2 sequences are increasing in proportion relative to other Omicron sublineages, there is still a reported decline in overall cases globally," the WHO says.

In other words, we should be worried about BA.2 but not panicked into thinking a whole new wave of the pandemic is about to break over us. It's more of roughly the same.

The pandemic has not ended but it continues to fade. It may vary in intensity but the trend is downwards, particularly if we keep getting vaccines and boosters, and taking elementary precautions like avoiding crowds, and donning masks as necessary.

Although evidence is limited, there is no data so far to suggest that BA.2 causes more severe illness than its precursor variants.

A good way of looking at this was to compare Britain with Denmark when the dominant variant of Omicron was BA.1 in Britain and BA.2 in Denmark. There was very little difference in the number of hospitalisations in the two countries.

The efficacy of existing vaccines is still being studied but the early indications are they remain effective against the new subvariant.

The evidence emerging from the UK indicates the vaccines in use in Australia are effective against BA.2, both in preventing infection and also preventing serious illness among those who do get infected.

But just as with the original Omicron, the vaccines and boosters wane in their protection.

"After three doses, we do get some protection against infection, but that wanes quickly over time," said Professor Adrian Esterman, of the University of South Australia.

"Both BA.1 and BA.2 are much milder than previous variants, with very much lower rates of hospitalisation. So, although many more people will be infected with BA.2 because it is so contagious, this will not necessarily be reflected in massive increases in hospitalisation because of its mildness, and also the fact that it is younger people mostly now getting infected, and they tend to have milder illness."

Annoyingly, it will not, says Paul Griffin, an epidemiologist at the University of Queensland.

"With such high levels of transmission, the virus has abundant opportunity to reproduce and for errors or mutations to continue to arise," he said.

"The way to address this, of course, is to try to slow transmission and reduce the susceptible pool of hosts in which the virus can freely replicate.

"Strategies such as social distancing and mask-wearing, as well as increasing vaccination rates globally, will slow the emergence of new variants and lineages."

On top of that, there already is a variant of Omicron BA.2, although BA.3 doesn't seem to have appeared in Australia yet.

The message from doctors and disease experts remains: get vaccinated and get a booster.

"My view is that people aren't taking precautions anymore and people are getting complacent about COVID," said Dr Andrew Jeremijenko, medical director of the Aspen Medical Group.

"We are seeing these long-term effects from COVID. It's still a serious disease but there appears to be a complacency around getting a booster."