• Thursday, September 28, 2023
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From immune evasion to vaccine escape, Delta Covid variant poses greater risk

From immune evasion to vaccine escape, Delta Covid variant poses greater risk

Like a new sheriff in town, the latest coronavirus variant, Delta, is sweeping through the world with a fierce attack on immunity acquired through either earlier infection or vaccination.

It is quietly slipping through vaccinated people who may not show signs of infection but can still infect others, leading to a dangerous impact on unvaccinated people. In its trail are rising hospitalization levels and death.

A clear statement from the behavioural pattern of this new strain as affirmed by even the World Health Organisation is that: it poses a greater risk with 30 to 60 percent more transmissibility than other variants of concern.

On average, an infected person will need eight times higher concentrations of antibodies to fight off the new version of the virus compared to the old ones, Morgan Chetty, a professor of health sciences stated in a piece of expert insight.

The third wave in South Africa, along with neighbouring Namibia, seems to be the worst yet, attributable to the Delta variant as they see up to 30,000 average new cases. In Uganda, the variant was detected in 97 percent of samples while 136 students tested positive for this Covid-19 variant in Ghana.

It is already rendering some of the most efficacious vaccine brands less effective with individuals showing waning immunity even after vaccination.

The B.1.617 (Delta) lineage was identified in October 2020 in India and has since then become dominant in some Indian regions and the UK and further spread to more than 100 countries.

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Research published by Nature, a science journal shows that the lineage includes three main subtypes: B1.617.1, B.1.617.2 and B.1.617.3, harbouring diverse spike mutations, which may increase their ability to evade immunity.

The study isolated an infectious Delta strain from a traveller returning from India and examined its sensitivity to monoclonal antibodies (mAbs) and to antibodies present in serums from COVID-19 convalescent individuals or vaccine recipients, in comparison to other viral strains. The researchers found that Delta was resistant to neutralization by some domains, which should normally cripple its effect.

Serums from convalescent patients collected up to 12 months post symptoms were fourfold less potent against the Delta variant, relative to the Alpha variant (B.1.1.7).

Serum from individuals having received one dose of Pfizer or AstraZeneca vaccines barely inhibited the Delta Variant. Administration of two doses generated a neutralizing response in 95 percent of individuals, with antibodies three to fivefold lower against Delta than Alpha.

As a result, the study concluded that Delta spread is associated with an escape to antibodies.

Chetty, a professor at the University of KwaZulu Natal, South Africa agrees also that escape-mutations may drive new resurgence, citing how the B1.1351 variant first identified in South Africa developed changes in the genetic code that makes it more menacing than the original virus. The version contains changes to the re-grow of the spike protein that human antibodies target to fight the virus.

“The newly reported variants carry the E484K mutation. The mutation was also found in the B.1.1.7 variant that originally was detected in the UK and the B.1.351 and B.1.128 variants that emerged in South Africa and Brazil repeatedly,” Chetty explained.

“The E484K mutation, which scoops a negatively changed antibody and effectively destroys the binding site. This is likely to make it difficult for antibodies elicited by the old variant to bind the new variant. E484K is called an escape because it helps the mutation escape the immune protection and the virus can slip past the immune defence.”

Another source, he said could drive escape mutation is the incomplete protection by the vaccine. More variants are found all over the world. Many of them do not significantly change how the virus behaves but some are more potentially dangerous. They make the virus more contagious and could make it more lethal or better at escaping existing vaccines.

The newest variant of major concern found in India has had a catastrophic impact on infections, mortality and has overwhelmed India’s health system. “The spread of these variants could mean that the Covid-19 pandemic could be here to stay and maybe the reason why vaccine escape is a major concern,” Chetty said.

Nigeria’s unvaccinated at risk

More than 99 percent of Nigeria’s population remains unvaccinated and the country is now among 16 countries that have reported the appearance of the Delta.

“The variant was detected in a traveller to Nigeria, following the routine travel test required of all international travellers and genomic sequencing at the NCDC National Reference Laboratory, Abuja,” the National Centre for Disease Control recently said.

The NCDC has urged all Nigerians to ensure strict adherence to public health and social measures in place. It advised that public health and social measures such as physical distancing, frequent handwashing and proper use of facemasks should be followed to prevent infections and save lives.

Given the global risk of spread of the Delta variant, the NCDC said positive samples from international travellers to Nigeria are frequently sequenced as part of Nigeria’s COVID-19 response.

The Nigerian government some months ago, placed travel restrictions on countries experiencing a surge in cases associated with variants of concern: India, South Africa, Brazil, and Turkey.

NCDC has now urged states to ensure sample collection and testing for COVID-19 is accessible to the public. Public settings such as schools with accommodation facilities, workplaces and camps should utilise the approved Antigen-based Rapid Diagnostic Test (RDT) for rapid testing of their population.

Babajide Sanwo-Olu, governor of Lagos State, Nigeria’s epicentre of the disease, also noted that the state had begun to see a steep rise in daily cases, with the positivity rate jumping from 1.1 percent at the end of June to 6.6 percent as of July 8th.

The general mood is being adjusted more in corporate settings than other places, and if the pattern of old strains emerging in Nigeria is anything to go by, the country might as well scale through without huge losses. However, only time will tell if ‘luck’ will be enough this time around.