TY - JOUR T1 - SARS-CoV-2 B.1.617.2 Delta variant emergence and vaccine breakthrough JF - bioRxiv DO - 10.1101/2021.05.08.443253 SP - 2021.05.08.443253 AU - Petra Mlcochova AU - Steven Kemp AU - Mahesh Shanker Dhar AU - Guido Papa AU - Bo Meng AU - Swapnil Mishra AU - Charlie Whittaker AU - Thomas Mellan AU - Isabella Ferreira AU - Rawlings Datir AU - Dami A. Collier AU - Sujeet Singh AU - Rajesh Pandey AU - Robin Marwal AU - Meena Datta AU - Shantanu Sengupta AU - Kalaiarasan Ponnusamy AU - V.S. Radhakrishnan AU - Adam Abdullahi AU - Niluka Goonawardne AU - Jonathan Brown AU - Oscar Charles AU - Partha Chattopadhyay AU - Priti Devi AU - Daniela Caputo AU - Tom Peacock AU - Dr Chand Wattal AU - Neeraj Goel AU - Raju Vaishya AU - Meenakshi Agarwal AU - The Indian SARS-CoV-2 Genomics Consortium (INSACOG) AU - The CITIID-NIHR BioResource COVID-19 Collaboration AU - Antranik Mavousian AU - Joo Hyeon Lee AU - Wendy S. Barclay AU - Samir Bhatt AU - Seth Flaxman AU - Leo James AU - Partha Rakshit AU - Anurag Agrawal AU - Ravindra K. Gupta Y1 - 2021/01/01 UR - http://biorxiv.org/content/early/2021/06/28/2021.05.08.443253.abstract N2 - The SARS-CoV-2 B.1.617.2 (Delta) variant was first identified in the state of Maharashtra in late 2020 and has spread throughout India, displacing the B.1.1.7 (Alpha) variant and other pre-existing lineages. Mathematical modelling indicates that the growth advantage is most likely explained by a combination of increased transmissibility and immune evasion. Indeed in vitro, the delta variant is less sensitive to neutralising antibodies in sera from recovered individuals, with higher replication efficiency as compared to the Alpha variant. In an analysis of vaccine breakthrough in over 100 healthcare workers across three centres in India, the Delta variant was responsible for greater transmission between HCW as compared to B.1.1.7 or B.1.617.1 (mean cluster size 3.2 versus 1.1, p<0.05). In vitro, the Delta variant shows 8 fold approximately reduced sensitivity to vaccine-elicited antibodies compared to wild type Wuhan-1 bearing D614G. Serum neutralising titres against the SARS-CoV-2 Delta variant were significantly lower in participants vaccinated with ChadOx-1 as compared to BNT162b2 (GMT 3372 versus 654, p<0001). These combined epidemiological and in vitro data indicate that the dominance of the Delta variant in India has been most likely driven by a combination of evasion of neutralising antibodies in previously infected individuals and increased virus infectivity. Whilst severe disease in fully vaccinated HCW was rare, breakthrough transmission clusters in hospitals associated with the Delta variant are concerning and indicate that infection control measures need continue in the post-vaccination era.Competing Interest StatementThe authors have declared no competing interest. ER -