New Delhi: While the entire nation is reeling under the impact of the second wave of Coronavirus, B.1.617 variant & its lineage B.1.617.2 are being said to be primarily responsible for surge in cases with high transmissibility of 50% more than Alpha variant (B.1.1.7).
This has been derived from a study by INSACOG (Indian SARS-CoV-2 Genome Sequencing Consortia ) & National Centre for Disease Control (NCDC).
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 were primarily responsible for the surge in Covid-19 cases with a high transmissibility of 50 per cent more than Alpha variant (B.1.1.7) found in 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 points at how the Alpha variant was responsible for a higher case fatality ratio as compared to the Delta variant or the virus dominant first identified 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 further clarifies that the increase in Covid-19 deaths was associated with the collapse in healthcare system and not because of the variant.
The study also says that it was the Delta variant that led to several infections even among vaccinated individuals. “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 viral load of B.1.617.2 appears to be higher than B.1.1.7 and based on data from India and UK, so does vaccination breakthrough rate.
“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 advised.
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