CORONAVIRUS: WHAT ARE VARIANTS OF CONCERN?
Recently, WHO has named variant of SARS CoV-2 B 1.617.2 as variant of concern. This variant is also referred as double mutant variant
MORE ABOUT VARIANTS OF CONCERN
Mutation – If manuscripts are copied by hand repeatedly, spelling errors are common. Similarly, when ‘genetic scripts’ encoded in DNA or RNA are copied repeatedly for virus replication, errors do occur.
o RNA viruses are more error-prone than DNA viruses. SARS-CoV-2 genome is singlestranded RNA, and errors — in biology, mutations — occur frequently.
o SARS-CoV-2 is new in humans and as it spreads, mutations are very frequent. Emerging variants with higher transmission efficiency become dominant, tending to replace others.
o Such frontrunners emerge in different geographic communities where the virus is epidemic, spreading widely.
Nomenclature schemes of virus – There are three different schemes of nomenclature of SARSCoV- 2 variants. The widely used one is the ‘Phylogenetic Assignment of Global Outbreak Lineages’ (PANGOLIN) that uses a hierarchical system based on genetic relatedness – an invaluable tool for genomic surveillance.
o Variant lineages are at the emerging edge of the pandemic in different geographies. Lineage B is the most prolific. The variants in circulation are B.1; B.1.1; B.1.1.7; B.1.167; B.1.177; B.1.351, B.1.427 and B.1.429. Lineage P.1 has deviated from the original B.
o Variants in India include the so-called double mutant B.1.617 spreading in Maharashtra and B.1.618 spreading in West Bengal.
Variants of Concern’ (VOC)
o The ‘concern’ in VOC comprises three sinister properties – transmission efficiency, disease severity and escape from immunity cover of vaccination.
o In many countries, including India, the VOC, by virtue of increased transmissibility, have kicked off new wave(s) of epidemic transmission.
o Unfortunately, at that precise time, as case counts were low, there was widespread relaxation of COVID-appropriate behaviour. Together, this has contributed to a rapidly ascending second wave — daily numbers far exceeding those during the earlier wave.
o The third concern is regarding the immunity cover offered by vaccination using antigens made from D614G variant — which applies to most vaccines in current use.
Lowered efficacy of vaccines was found more with the South African and less with the Brazil variant.
o Hence, reinfection can occur in spite of immunity by earlier D614G infection or vaccination. Vaccine efficacy may be lower now than what was determined in phase-3 trials as VOC were not then widely prevalent.
o Fortunately, mRNA (Pfizer and Moderna) vaccines have broader immunity for different reasons, and they protect better against these two variants.
Lessons for India – An important lesson the pandemic has taught us in India is the critical importance of biomedical research and capacity building – for saving lives and economic growth.
o We need a foundation of broad-based research, in universities, medical colleges and biotechnology companies, all of which must be funded, encouraged, appreciated, and talent rewarded.
o While some endeavours have been initiated, they must take off in a big way, and India must invest heavily in biosciences