Eversince its origin, the SARS COV-2 virus is on the continuous phase of becoming a pandemic and time to time change in its genetic structure making reinfection a possibility. Viruses usually acquire mutation and sometimes these mutations lead to development of variants which may show changes in their transmissibility and lethality. There are various nomenclatures given to these mutations and nearly 5000 mutations were detected ever since the diagnosis of COVID.
WHO (World Health Organization) had developed a new method to detect which of these mutations to be given importance and they divided them to “variants under investigation” (Variants of interest), “Variant of concern” and “variant of high consequence” depending on the potential effects of the emergent variant like:
- More transmissibility
- Aggrevated morbidity and mortality
- Ability to escape from diagnostic tests
- Decreased susceptibility to antiviral drugs
- Decreased susceptibility to neutralizing antibodies, either therapeutic (e.g., convalescent plasma or monoclonal antibodies) or in laboratory experiments
- Ability to evade natural immunity (e.g., causing reinfections)
- Ability to infect vaccinated individuals
- Increased risk of particular conditions such as multisystem inflammatory syndrome or prolonged COVID infection
- Increased affinity for particular demographic or clinical groups, such as children or immunocompromised individuals.
Of these the important “Variants of concern” include the Alpha, Beta, Gamma and delta variant. There were various nomenclatures proposed initially for identifying these mutations like PANGO (Phylogenetic Assignment of Named Global Outbreak) lineages or GISAID clades or Nextstrain clades. But after months of discussion, WHO decided to label these mutations in Greek letters to prevent geographical and political conflicts.
With various strains as described increase, one can notice the wild virus responsible for most of the 1st wave of pandemic called as D614G. In India, there was an upsurge caused by the mutation N440K which is responsible for many infections in South India. Later newer mutations occurred leading to new waves and few mutations increasing transmissibility and escape from vaccines and therapies. Presently there are upsurge of cases in Africa, Australia, Indonesia and UK, the delta variant or newer mutations considered as suspect.
Its important to know about these strains as we may need to change the vaccines which are efficacious to a particular strain and also the placement of vaccines. Regarding placement of vaccines the distance varied with vaccine companies and countries. India initially placed for COVISHIELD, the 2 jabs at a gap of 4-6 weeks but later on based on a scientific article published in Lancet decided to increase the duration of jabs between 12 – 16 weeks. But with entry of Delta variant, UK decreased the duration between 2 jabs to 8 weeks.
Delta variant was the predominant variant in India during the second wave. The delta variant is a collection of 13-15 mutations of which several are of concern. But recently it picked up a new mutation in K417N and now its been designated as AY.1 variant or delta plus. A study by Rockfeller university found that these mutations diminished the efficacy of antibodies of mRNA vaccines. Now delta variant had spread to nearly 98 countries pushing few countries like Indonesia into medical emergency. Also the delta variant had been found to have more affinity to lung tissue which leads to more patients having pulmonary complications.
Also with less efficacy of some vaccines like the Chinese Sinovac against the new variants, few countries like Turkey and UAE had initiated to give booster dose and few other countries like Thailand and Indonesia are in the thought of considering a booster dose. The proportion of cases with variants of concern increased from 10.31% in May 2021 to 51% on June 20, 2021 in India. Variants of Concerns with public health importance detected in community samples in India:
• Alpha – 3,974
• Beta- 149
• Gamma- 1
• B.1.617, Delta and Kappa – 16,260 as of June 26, 2021.
With these increase in variants it becomes necessary to do genome sequencing of at least 5% of positive samples by laboratories under INASCOG (Indian SARS- CoV-2 genomics Consortium ) and update the data to GISAID ( global initiative on sharing avian influenza data).
With these it becomes necessary to keep an eye on the mutations the virus is undergoing to be ready to fight back further waves.
