Mumbai: What exactly is Maharashtra's 'double mutant' strain?

Antigen tests being conducted at the Lokmanya Tilak Terminus Railway Station on Saturday. Pic/Sayyed Sameer Abedi

A fortnight ago, health ministry officials declared that a new double mutant strain of the Coronavirus - its formal scientific classification being B.1.617 - had been found in India. This variant has grown to become common across India and is touted to have accelerated the spread of the virus across different states. But what exactly is this double mutant strain and what is its relation to the surge in cases being experienced in some states like Maharashtra and Punjab?

According to Dr N K Ganguly, former director of the Indian Council of Medical Research (ICMR), the major mutational virus being found in approximately 76 per cent of India's 10,000+ samples is the B117 UK variant. "This strain is 70 per cent more transmissible. It doesn't target older people who are getting vaccinated and/or sitting at home. It targets people above the age of 29 years, who are asymptomatic and who step out of home regularly to work. The other worrisome variants are the Brazilian variants and South African variants. However, the first-ever double mutant strain was found in California… whose positioning is such that they cannot be suppressed by vaccines."

"The double mutant strain has been found in 206 samples in Maharashtra out of a total of 10,000+ sequencing samples," said Ganguly. "Essentially, this strain is a combination of two variants - E484Q and L452R. The latter one is the most worrisome one. These two mutants, found only through deep sequencing, are such that they are not affected in the same manner [as other variants] by antibodies. Lots of mutational viruses don't survive; most of them go away but some mutants end up establishing themselves. The L452R variant targets a particular gene that is found in people living in India. We do not know how well the vaccine(s) works on this variant. These mutational strains are new, which is why it is only after the results of the current stage of vaccine trials come in that will we know the effect it has on this strain." He added: "The HIA-A23 is a susceptible gene that may or may not be able to escape mutation through immune pressure. Vaccine(s) may work but with reduced efficacy."

The double mutation causes a phenomenon called "immune escape" wherein the virus manages to slip past the body's immune defenses and increases infectivity. So far, these mutations do not have any previously catalogued variants of concern, said a health ministry official.

Ganguly concluded that the efficacy of vaccines against this double mutational strain only has "test-tube data" for now, but once the new vaccine trial results come in, we will have a clearer idea of its efficacy. "Test tube data is not enough and we need to have results in the field as well," he said.

On the other hand, the government has said that both vaccines are effective against double mutation. "However, India has not yet conducted any study on how vaccine efficacy is influenced by variants, although international studies have shown reduced efficacy of vaccines towards certain variants."