‘Gold standard’ RT-PCR test and Rapid Antigen Test (RAT) continue to work well and there is no evidence whatsoever to show that any of the existing COVID variants could escape the diagnostics, including the currently-dominant Delta variant across the world, said scientists of Centre for Cellular and Molecular Biology (CCMB).
“RAT is designed against the ‘N’ gene which is relatively well conserved in any of the variants and so is less likely to escape. Going by the trend, Delta variant too is unlikely to escape. RT-PCR tests are designed across the genome and have multiple targets for the virus so chances of any variant escaping is very rare,” informed scientist Divya Tej Sowpati at a webinar organised recently.
While there have been instances of RT-PCR tests showing ‘false negatives’, he suggests the individual concerned stay quarantined within a week in case of any obvious symptoms like fever, cold, body pains, and redo the test.
“It is extremely rare for two ‘false negatives’ to come out of RT-PCR testing, hence most testing kits continue to be valid,” he said.
Dr. Tej said while he was not in vaccine-based research, he could say that there was no co-relation in stating that variants which escape the diagnostic tests can also prevent the anti-bodies formation due to vaccination. “Protection from anti-bodies depend on the spike proteins and the likes,” he said, in the online event organised by PATH and Rockfeller Foundation.
Virus variants do have an “advantage” in breaking the vaccine immunity but the vaccines are definitely effective against “severe or symptomatic form of disease at 97% infection, so the for the variant advantage stops there,” said the scientist.
Lab consortium
The recently-formed consortium of eight labs is to help upscale coronavirus genomic surveillance and to complement the national efforts led by INSACOG - Indian SARS-CoV-2 Genomics Consortium which will help in genome sequencing of the virus. This is to keep a watch out for virus ‘variants of concern’ - showing immune escape mutations, potential to escape diagnostics and changes in receptor binding to the hots and of ‘virus variants of interest’ - evidence of increased infectivity, possibly associated with severe disease and evidence of vaccine escaping immunity - among the population.
The effort is to collect COVID samples from a wide geographic spread but at times more samples are collected from areas where there was specific outbreaks, super spreader events, more cases being reported from a particular hospital and so on, explained Dr. Tej.