A new variant of COVID has arrived in Australia, and health authorities are monitoring its spread very closely.
BA.2, as it has become known, is actually a subvariant of Omicron, and thus has not been allocated a new variant name.
Victoria’s COVID-19 response commander Jeroen Weimar says genome sequencing has shown a handful of cases have been detected in the state. As of last Friday, there were 22 known cases of BA.2 across Australia.
With Victorian students returning to school, the state’s Health Minister Martin Foley wants as many eligible students as possible to get vaccinated. “We want to see every one of those who are eligible to get vaccinated,” he says. “That’s our target. That’s how we’re going to drive down the Omicron variant.”
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Subvariant BA.2 has been reported in more than 50 countries, and in some of those it appears to be spreading faster than the original Omicron variant, an indicator that it could be more infectious.
Of the 18,000 cases detected worldwide, the majority have been in Denmark.
Should you be worried about the BA.2 subvariant?
With such a low number of known cases, it is too early to tell whether BA.2 is likely to cause concern among health authorities. But early analysis of the cases in Denmark suggests the hospitalisation rate is the same as it was for the original variant of Omicron, BA.1. Associate professor of virology at Rockefeller University, Theodora Hatziioannou, says that subvariants are typical of all viruses.
Viruses mutate all the time, and diversification within each variant is very common. Professor Francois Balloux, professor of computational systems biology and director at the UCL Genetics Institute, put forward the Delta variation asthe perfect example of that: “The previously globally dominant Delta variant D comprised over 200 sub-lineages before it got replaced by Omicron,” he says. “Additional Omicron sub-lineages will undoubtedly be described in the future.”
At this stage, the World Health Organization (WHO) has not designated BA.2 a variation of concern.
What is a ‘variation of concern’?
The WHO uses various criteria to determine the seriousness of a variant. In general terms, a variant that has mutations suspected or known to cause significant changes, and is circulating widely (e.g., known to cause many clusters of infected people, or found in many countries) is designated as a ‘variant of interest’.
A variant of interest becomes a variant of concern if it is known to spread more easily, cause more severe disease, escape the body’s immune response, change clinical presentation or decrease effectiveness of known tools, such as public health measures, diagnostics, treatments and vaccines.
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BA.2 has been referred to by some as a ‘stealth’ variant, because it lacks a signature deletion mutation present in BA.1, which PCR tests could use to figure out if a sample was Omicron or not. PCR tests that relied on spotting this deletion missed classifying BA.2 as Omicron.
But this is not a cause for concern, says Professor Seshadri Vasan, COVID-19 project leader at the CSIRO.
Are the current COVID vaccines effective against BA.2?
Again, because this subvariant is new, data on vaccine effectiveness is limited, but early research from the UK indicates vaccines provide similar protection against BA.2 as they do against the original BA.1 variant.
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Dominic Dwyer, the director of NSW Health Pathology at Westmead Hospital, believes that with researchers in Australia monitoring the COVID-19 situation closely, there is no cause for the general public to be concerned about BA.2. “At this stage, there’s nothing yet to say that it is different from ordinary Omicron.”
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