Exclusive: Delta variant primary cause behind second Covid-19 wave, finds govt study

In a study carried out by scientists of INSACOG (the consortium of labs endeavor genome sequencing in India) and National Centre for Disease Control (NCDC) on the explanations behind the second wave that swept North India, has revealed that regardless of Delhiites having sero positivity of over 56 per cent, they received little safety in opposition to the Delta variant that took over the nationwide capital March 2021 onwards.


About the sharp and devastating spike in Delhi, the study says, “After touching the high of almost 9,000 cases daily and a positivity rate of about 15 per cent during the third wave in November 2020, new cases steadily declined, with only 1 per cent positivity between December 2020 and March 2021. This reversed and started increasing from third week of March, 2021, shooting to 30 per cent by end of April, with almost 30,000 cases being reported per day.”


The B.1.617 variant and its lineage B.1.617.2 had been primarily accountable for the surge in Covid-19 circumstances with a excessive transmissibility of fifty per cent greater than Alpha variant (B.1.1.7) discovered within the UK, the study says.

“Detection of B.1.1.7 VOC (variant of concern) was minimal until January 2021, increasing to about 20 per cent in February and 40 per cent in March 2021. This was associated with slight increase in Rt from about 1.2 to 1.6. B.1.617 lineages increased from below 5 per cent in Feb 2021 to about 10% in March before overtaking B.1.1.7 in April and rising to about 60 per cent of all samples. The sub-lineage B.1.617.2, in which the escape mutation E484Q is lost and a new mutation T478K is gained, showed the maximum rise going from less than 10% of B.1.617 to about 80 per cent. The rise of B.1.617, more specifically B.1.617.2, was paralleled by a large increase in positivity rate,” the study says.


The study factors at how the Alpha variant was accountable for the next case fatality ratio as in comparison with the Delta variant or the virus dominant first recognized in India.

“The CFR (case fatality rate) values, which were constant from December till February, 2021, witnessed a significant decrease with a simultaneous increase from March. This may be due to the sudden decrease of B.1.1.7 in the Delhi region which reportedly causes high CFR.”

“The case fatality rate was rising again towards the end of this period. Since CFR may be due to an amalgamation of multiple factors, including the short-term collapse of the healthcare system, there is currently no clear evidence linking B.1.617.2 to the change in CFR.”

The study additional clarifies that the rise in Covid-19 deaths was related to the collapse in healthcare system and never due to the variant.


The study additionally says that it was the Delta variant that led to a number of infections even amongst vaccinated people. “B.1.617.2 was over-represented and B.1.1.7 was not even detected in vaccination breakthroughs, suggesting higher breakthrough risk of B.1.617.2 compared to B.1.1.7.”


The study says that the April 2021 outbreak in Delhi was preceded by different outbreaks in Kerala, Maharashtra and Punjab. While no variant of concern was recognized in Kerala in January 2021, the outbreak in Maharashtra has been associated to B.1.617.1 and in Punjab to the introduction of B.1.1.7.

These had been discovered to be phylogenetically associated, with a robust evolutionary connection between Delhi and Punjab for B.1.1.7 and between Delhi and Maharashtra for B.1.617 lineages.


The study says that the viral load of B.1.617.2 seems to be increased than B.1.1.7 and based mostly on information from India and UK, so does vaccination breakthrough fee.

“While immune escape seems less for B.1.617.2 compared to B.1.351 or P.1 overall, we note that B.1.617.2 is capable of creating very fast-rising outbreaks with vaccination breakthroughs. We would re-emphasize that prior infections, high seropositivity and partial vaccination are insufficient impediments to its spread, as seen in Delhi, and strong public health response will be needed globally for its containment,” the authors have suggested.

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