Stealth Omicron sub-variant spreads 1.5 times faster than the original, study warns
THE NEW Covid sub-variant BA.2 spreads 1.5 times faster than it’s “sister” Omicron, a study has warned.
Early calculations come from the top infectious disease authority in Denmark, where the majority of the world’s BA.2 Covid cases have been detected.
The Statens Serum Institut (SSI) technical director Tyra Grove Krause said: "There is some indication that it is more contagious, especially for the unvaccinated, but that it can also infect people who have been vaccinated to a greater extent.”
It comes as data from the UKHSA last week suggested the strain was more transmissible, but "no more severe" than the original Omicron variant that is still dominant in the UK.
Denmark was one of the first countries where BA.2 initially spread, meaning its data may give the clearest picture of the strain available.
It has reported some 20,000 infections of the strain compared to the UK’s 2,500.
But even if BA.2 can spread faster, it is not clear how this would play out in a population that has high immunity - either through vaccination or prior Omicron infection.
An initial analysis by SSI showed no difference in the risk of hospitalisation for BA.2 compared to BA.1 - the original Omicron strain - reported.
Krause said: "Overall, we must say that the epidemic is still growing and that there is still a risk that infection rates will increase further in the coming weeks.
“Therefore, there is also a risk that the number of admissions will increase. ”
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"On the other hand, we expect the admissions to be milder than before due to vaccination and the Omicron variant".
The original Omicron strain, which BA.2 is very closely related to, is much milder than previous variants.
Those infected with Omicron are around 50 per cent less likely to end up in hospital compared to those who had Delta.
Scientists are not overly concerned about the emergence of BA.2 because as of yet, there are no signals it will drive up hospitalisations.
British epidemiologist Professor Tim Spector said he believes BA.2 is “not more severe” based on stable hospitalisations in Denmark.
What’s more, UK data show that three vaccine doses are highly protective against BA.2, with the booster shot driving efficacy against hospitalisation to 70 per cent.
Its higher transmissibility, however, could mean that Omicron Covid waves will not dwindle as soon as hoped.
Top UK health chiefs had said the Omicron wave would likely consist of a dramatic spike in cases, before a very fast fall.
And the forecasts were correct - after a huge surge in December, peaking in early January, Covid infections in the UK swiftly came down again.
But recently, after the detection of BA.2, the slowing has stalled. Cases are now flat at roughly 90,000 per day.
Eric Topol, the director of Scripps Research Translational Institute, said of BA.2: "Its increased transmissibility will prolong the Omicron wave in many places."
The recent stabilising of Covid rates is also due to schools returning and infections in children spilling out to parents, too, experts say.
It comes after The UK’s health agency also said that BA.2 “has an increased growth rate compared to BA.1 in all regions of England”.
A report published on Friday warned: “While growth rates can be overestimated in early analyses of a new variant, the apparent growth advantage is currently substantial.”
Analysis of cases so far shows that people with BA.2 are more likely to pass the strain onto people they live with, called the secondary attack rate.
Data reveals that although BA.2 has only been around for a month or so, it has overtaken Delta.
claims BA.2 accounted for an estimated 2.8 per cent of cases in the UK in the week to January 22, up from 0.8 per cent a week prior and against Delta’s 0.2 per cent.
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It comes after reinfections in the UK were counted for the first time in the pandemic.
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An addition of 588,114 cases were added to the Government dashboard yesterday due to the inclusion of reinfections, which had previously not been part of the tally.
On top of this, 173,328 formerly unreported cases were added on, and the daily tally of 92,368.
