More dangerous variants are likely to emerge and spread across the world, according to the WHO
There were predictions that 2021 would become the year of novel coronavirus disease (COVID-19) variants. It has.
The Delta variant, implicated in India’s second wave of infections, has become the most dominant COVID-19 variant circulating in the world and has been reported from 111 countries.
The World Health Organization (WHO)’s International Health Regulations (2005) Emergency Committee indicated July 15, 2021 that more dangerous variants are likely to emerge and spread across the world.
As of now, WHO has identified four ‘variants of concern’. The Delta variant was first isolated in India in October 2020 and was labelled as a variant of concern May 11, 2021. It now dominates the world.
In the United Kingdom, it forms 98.9 per cent of the sequenced samples over the last month. In the United States, it is 59.2 per cent of the sequenced samples. Mutations have helped the virus dominate across the world.
“Compared to the Wuhan strain, the Delta variant has 9 mutations in the spike proteins that help the virus gain entry into the cell,” says Olivier Schwartz, head of Virus and Immunity Unit at Institut Pasteur, France.
Francis P Wilson, associate professor of medicine and director, Clinical and Translational Research Accelerator at Yale University School of Medicine, Connecticut, United States, said:
The Delta variant is significantly more transmissible than the original (Wuhan) SARS-CoV-2 and the average infected person can infect more people, spreading the disease faster and overwhelm local healthcare systems.
So far, it is unclear if the Delta variant is more pathogenic than the other variants. Death rates from it seem similar to those from the other variants, which is good news.
The data is not yet clear about immunogenic breakthrough which indicates whether people who have immunity from prior infection or vaccination are at risk from the Delta variant or not, explains Wilson.
High maintenance variant
As more and more mutations accumulate, SARS-CoV-2 could come to a point that it becomes a new virus. But has this time come for the novel coronavirus? “No, it has not,” says Satyajit Rath, immunologist and visiting professor at IISER Pune.
While it is true that a large percentage of genetic sequence changes will ‘make’ a new virus, the proportion of changes in SARS-CoV-2 variants is very small so far, Rath said.
The proportion of change in the genetic sequence (of genes) of the virus indicates its familial lineage relationships. It does not indicate or correlate with the changes in virus behaviour (such as more transmissibility), since changes in behaviour depend on the locations of the genetic changes, rather than on the amount of the genetic changes, he added.
Despite these mutations, there is evidence that vaccination can protect from this variant even if the levels of protection have fallen.
Researchers from the Indian Council of Medical Research studied 677 vaccinated people who contracted COVID-19. Genomes of 511 of them were sequenced and this indicated that Delta variant sickened 86 per cent of them.
These people had received Covaxin, Covishield or the Sinopharm vaccine. All the vaccines seemed to have prevented severe cases. Only 9.8 per cent of the vaccinated people had to be hospitalised and only 0.4 per cent of them died. The preprint was published on the MedRxiv site July 15.
In the UK, blood and swab samples collected for the SARS-CoV-2 Legacy study were used to track the risk of infection in people vaccinated with the Pfizer / BioNTech vaccine. Researchers analysed antibodies in the blood of 250 healthy people who received either one or two doses of the vaccine, up to three months after their first dose.
They found that in people who had been fully vaccinated with two doses of the vaccine, levels of neutralising antibodies were five times lower against the Delta variant when compared to the original strain, upon which current vaccines are based. Importantly, this antibody response was even lower in people who had only received one dose, the researchers reported in The Lancet on June 3.
Similar studies done by the group using the AstraZeneca vaccine showed that the levels of neutralising antibodies were lower than those generated by Pfizer/BioNTech vaccines. This was published in The Lancet July 17, 2021.
Ensuring that vaccines are effective against the Delta variant is important as the risk of a third wave is imminent.
“Though the R value (reproduction number) is below 1 at present, it went up from the all-time-low of 0.78 between mid-May and late June to 0.88 by end-June,” Sitabhra Sinha, professor at the Institute of Mathematical Sciences, Chennai, said. The reproduction number is a measure of how contagious a disease is. If the R value is more than 1, each existing infection causes more than one new infection.
The R value then rose to 0.98 between July 6 and July 10 but then fell down from July 10-13 to 0.92. After July 13, the data is fluctuating too much to get a robust estimate but it looks like it is hovering around 0.95, Sinha estimated.
“We have to see whether it again comes close to 1 in the next few days and the longer it stays close to 1, the higher the risk of a chance event pushing a new increase in cases, the so-called third wave,” he said.
Experts say that vaccination is the only way out as new variants are likely to continue to emerge. However, vaccination levels remain low globally with only 25.9 per cent of the population receiving one dose of the vaccine.
In India, vaccination rates are low too and less than 24 per cent of the people have received one dose of the vaccine. Less than six per cent of people are fully vaccinated.
The country needs (and has needed from day one) equitable and rapid vaccination, so as to limit severe illness and misery and the appearance of the patchwork situation with populations with high and low levels of vaccination, said Rath.
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