Stealth ‘sister’ sub-variant will overtake Omicron within a month – but it’s just as mild, expert reveals

THE 'sister' sub-variant of Omicron is set to overtake the original within a month.

It is thought to be able to spread slightly faster - but currently isn't believed to be any more severe or dodge vaccines.

The proportion of Covid cases caused by “BA.2”, or "Omicron's sister", have quadrupled in seven days, scientists say.

The variant has spread to at least 40 countries since it popped up in November, mostly in Denmark, India and Sweden - but scientists don't believe it causes a more serious illness than the original Omicron strain.

Some 426 cases of the new variant had been confirmed in the UK as of January 21.

However, data from the  says there have been 1,845 cases so far, mostly in England. 

Professor Tim Spector, lead scientist on the ZOE COVID Study app, said: "Another emerging factor is that a new subtype of Omicron is taking over called BA.2, which is likely more infectious.

"One in 20 new cases had this variant last week, and as it's doubling every few days this should predominate within a month.

"The ZOE data has also seen more confirmed reinfections in recent weeks with  around seven per cent of new symptomatic cases having previously tested positive, suggesting a natural infection with Delta may not offer much protection."

Cases have risen in the past few days, with this thought to be sparked by schools going back.

Kids are largely unvaccinated and hadn't mingled much over Christmas, so they are only now catching Omicron in larger numbers.

Prof Spector said: "It [BA. 2] makes up five per cent of the UK data currently, if it goes on this trajectory it could well takeover within a month.

"What we know is yes it's more competitive, it's quite similar but also different and so far Denmark hasn't had a major problem with hospitalisations and deaths suggesting it's not more severe."

A string of positive studies show Omicron is milder than other strains in the vaccinated - with jabs expected to work against BA.2.

Health officials in Denmark, who have seen the most cases of BA.2 so far, say Covid vaccines are thought to still be as effective.

Prof Francois Balloux, Professor of Computational Systems Biology and Director, UCL Genetics Institute, UCL, said the two strains are “about 20 mutations apart”. 

It means anyone who has already had the fierce Omicron variant is likely to have “robust immunity” against the new one.

According to the symptom study data, there are currently 159,486 new daily symptomatic cases of Covid, an increase of ten per cent on last week.

Prof Spector warned cases are set to remain high until spring, with current new daily infections hovering around 100,000 in the UK.

He added: "The bounce back in case numbers just as we lift restrictions has come sooner than many expected.

"But it’s not surprising given that, throughout the pandemic, we’ve seen the end of school holidays repeatedly usher in a rapid rise in cases among children, which then cross over into parents and school staff.

"However, the good news is that most vaccinated infections are mild, with symptoms lasting on average for a shorter time overall than Delta and with less severe cases.

"It’s clear that Covid and its new variants will continue to have an impact on our day-to-day lives for some time.

"It’s crucial that we’re responsible with our new freedoms and help to keep case numbers down and prevent the virus reaching the more vulnerable groups.”

It comes as major Plan B Covid rule changes came into force in England today.

Restrictions that came back in last year have slowly been ebbing away - with working from home rules stopped last week.