PremiumThe sub-variants of Omicron-BA.5 and BA.5 are more transmissible, and can dodge some of the immune protection conferred by previous infection and vaccination, as per the scientists
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It's been more than two years since the Covid-19 pandemic upended the lives of people, but still, there has been a constant fear of a new wave as the virus has continued to mutate in different forms. Currently, the two common variants that are dominating in the world are the offshoots of the Omicron virus.
Several studies, including World Health Organization (WHO), have asserted that the sub-variants of Omicron-BA.5 and BA.5 are more transmissible, and can dodge some of the immune protection conferred by previous infection and vaccination.
According to Nature's magazine, the rise BA.4 and BA.5 — as well as that of another Omicron offshoot in the US — could mean that SARS-CoV-2 waves are beginning to settle into predictable patterns, with new waves periodically emerging from circulating strains.
“These are the first signs that the virus is evolving differently" compared with the first two years of the pandemic when variants seemed to appear out of nowhere, Tulio de Oliveira, a bioinformatician at Stellenbosch University in South Africa told the magazine.
Omicron's BA.4 and BA.5 subvariants emerged in mid-December 2021 and early January 2022 in South Africa first, thereafter, they gradually spread to other countries. The two sub-variants of Omicron account for 60-75% Covid cases in South Africa at present.
The boost in transmissibility of Omicron varinats is similar in magnitude to the advantages that some other fast-spreading SARS-CoV-2 variants had over their predecessors, says Tom Wenseleers, an evolutionary biologist at the Catholic University of Leuven in Belgium. “Taking everything together and looking at all the data, it seems a sizeable new infection wave is certain to come."
Jesse Bloom, a viral evolutionary biologist at Fred Hutch, a research centre in Seattle, Washington, said that BA.4 and BA.5 are spreading faster than other Omicron lineages. Bloom said that the two sub-variants carry a key mutation called F486V in their spike proteins — the viral protein responsible for infection and the prime target of immune responses. Bloom’s team has previously found that this mutation could help variants to dodge virus-blocking antibodies.
Alex Sigal, Research Group Leader at Max Planck Institute for Infection Biology, Berlin stated that BA.5 and BA.5 are not dramatic but can cause trouble and lead to an infection wave.
Hospitalizations are slowly ticking up in South Africa — from a low of just under 2,000 people in hospital with Covid-19 in early April — but researchers say it’s too soon to tell whether BA.4 and BA.5 will put much pressure on healthcare systems.
The next Covid wave
Although BA.4 and BA.5 have been detected in several European countries, as well as in the US, researchers and scientists say the variants might not set off a fresh wave — at least right away.
If SARS-CoV-2 continues along the mutation path, its evolution could come to resemble that of other respiratory infections, such as influenza, as per the experts. In this scenario, immune-evading mutations in variants, such as Omicron, could combine with dips in population-wide immunity to become the key drivers of periodic waves of infection.
“What is still unclear is why they are more transmissible," he says. “
BA.4 and BA.5 both carry a key mutation called F486V in their spike proteins — the viral protein responsible for infection and the prime target of immune responses. Bloom’s team has previously found that this mutation could help variants to dodge virus-blocking antibodies.
BA.4 and BA.5’s capacity to escape immunity, although not dramatic, “is enough to cause trouble and lead to an infection wave" — but the variants are not likely to cause disease much more severe than was seen during the previous wave, especially in vaccinated people, Sigal said in a Twitter post. “They clearly have an advantage in antibody escape, which is one contributing factor in why they are spreading," says Bloom.
Hospitalizations are slowly ticking up in South Africa — from a low of just under 2,000 people in hospital with Covid-19 in early April — but researchers say it’s too soon to tell whether BA.4 and BA.5 will put much pressure on health-care systems. “The hospitals are empty in South Africa and we have high population immunity," says de Oliveira.
However,
Some parts of North America are also seeing the rise of other Omicron sub-lineages that have spike-protein mutations in some of the same places as in BA.4 and BA.5. One such variant — called BA.2.12.1 — also has the capacity to evade antibodies triggered by a previous Omicron infection and vaccination, according to the study3 led by Xie, and separate work by virologist David Ho at Columbia University in New York City.
