A new sub-strain of the Omicron variant of coronavirus, which has been spreading rapidly across the globe, has emerged as the latest challenge in taming Covid-19. The BA.2 sub-strain has been detected in at least 57 countries, according to the World Health Organization (WHO). A leading healthcare expert has said that people need to be cautious about it.

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“We should be cautious and monitor new information as it comes out, but we shouldn’t worry,” Dr Leana Wen, a professor of health policy and management at the George Washington University Milken Institute School of Public Health, told CNN.

She further said that BA.2 has replaced the very contagious original Omicron variant, known as BA.1, in some places.

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At the same time, Dr Wen said that Omicron won’t be the last variant of the coronavirus.

“Almost certainly not. New variants are popping up all the time, because that’s what viruses do: They mutate when they replicate,” she said, adding: “This is why real-time surveillance is so important, and it’s also why vaccination is key.”

How transmissible is BA.2?

As per the available data from various governments, especially in worst-hit Europe, the BA.2 sub-strain has gained ground in recent months. In Denmark, for example, people infected with BA.2 spread the virus to an average of 39% of susceptible household members, versus 29% for the original omicron variant. That’s in line with preliminary UK data.

However, the health experts have said that Omicron has not been as deadly as Delta.

But is BA.2 more dangerous than previous strains?

Not really, according to WHO. Based on evidence from Denmark, the WHO said this week that BA.2 doesn’t seem more severe than the original Omicron variant and its spread hadn’t led to unexpected spikes in hospitalisations.

The recent changes announced by the government in Denmark reflected the same, when Covid-19 restrictions were ended. The Danish government said that the disease no longer poses a threat to society, even as cases hit a record high.

Are vaccines effective against BA.2 sub-variant?

The latest data from Europe indicates that the existing vaccines are as effective against BA.2 as against the previous sub-variants. Though BA.2 is more contagious, vaccines blocked 13 per cent of cases 25 weeks after the second dose, a UK study showed.

The number increased to 70 per cent two weeks after a booster dose.

Differences between BA.2 and BA.1

The researchers said that BA.2 has 40 different mutations than the original sub-strain, including a key alteration in the spike region.

While the two are related, there are enough differences to drive a change in behaviour. The milder form of most Omicron cases in vaccinated people may leave those who recover still vulnerable to existing virus and future variants, according to researchers.

They further said BA.2 will prolong the Omicron-led wave of Covid-19. A potentially slower decline in cases could lead to higher hospitalisations and pose a problem for countries with lower vaccination rates.

Trevor Bedford, a computational biologist working at the Fred Hutchinson Cancer Research Center, said it’ll “create a substantially longer tail of circulation of Omicron”.

(With inputs from agencies)