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Curbing Delta: On the variant that drives India’s COVID-19 infections

Increasing vaccination and monitoring of new variants are essential in fighting the pandemic

August 23, 2021 12:02 am | Updated 12:52 am IST

The overall number of coronavirus cases in India is on a downward trajectory though around 35,000 cases continue to be added almost daily. Nearly three in four of these infections are from Kerala and Maharashtra with the former — once heralded as the model State in tackling the pandemic — contributing close to 60% of the national total. There may be several reasons why this is the case and one of the conjectures is that newer variants may be playing a significant role. A weekly update from the Indian SARS-CoV-2 Genomics Consortium (INSACOG), a repository of labs tasked with monitoring variants of the coronavirus, says that the Delta variant remains most responsible for the continuing spread of infections in India . The INSACOG collects a percentage of coronavirus-positive samples for analysis from all States and of the nearly 50,000 samples analysed for their genetic composition, about two thirds — 30,230 — were among the internationally classified Variant of Concern or Variant of Interest (VoC/VoI). Of these, nearly 20,000 were the Delta variant (AY.2) and about 5,000, its associated lineages (AY.1 and AY.3). Because they contain mutations that help the virus avoid detection by the immune system, the lineages of the Delta variant are driving spikes in infections worldwide. Globally, there are believed to be 13 sublineages of Delta with characteristic genetic mutations. AY.1, AY.2 and AY.3 are the predominant ones.

Concerning as this variant is, it should not be forgotten that the purpose of the existing vaccines is to prevent hospitalisation and mortality, and the limited evidence so far is that vaccine coverage has played a role in keeping hospitalisation in most States to manageable levels as well as allowing normalisation of economic activity. Unless there is a dramatic fall in susceptible hosts globally, it is unlikely that transmission will obliterate itself. India’s Drugs Controller General has now approved a three-shot vaccine, ZyCoV-D, for use in those 12 and above. The interim efficacy data of this vaccine shows that it has only 66% efficacy which is lower than what most of the other vaccines delivered in their trials. Zydus Cadila also has not published phase-3 results from the trials and so it is quite uncertain if the vaccine will meaningfully curb transmission but may well be effective in boosting India’s vaccine arsenal, cutting disease and saving lives. The INSACOG still monitors too few a proportion of coronavirus samples given that India has the second highest numbers globally. Improving coverage and increased vaccination continue to remain the best bets against the pandemic.

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