Transmission of B.1.617.2 Delta variant between vaccinated healthcare workers
Steven A. Kemp, Mark T. K. Cheng, William L. Hamilton, Kimia Kamelian, Himanshu Chauhan, Tanzin Dikid, Hema Gogia, Hemlata Lall, Kalaiarasan Ponnusamy, Kaptan Verma, Mahesh Shanker Dhar, Manoj Singh, Meena Datta, Namita Soni, Namonarayan Meena, Preeti Madan, Priyanka Singh, Ramesh Sharma, Rajeev Sharma, Sandhya Kabra, Sattender Kumar, Swati Kumari, Uma Sharma, Urmila Chaudhary, Sridhar Sivasubbu, Vinod Scaria, Chand Wattal, Jaspal Kaur Oberoi, Reena Raveendran, Sandip K. Datta, Saumitra Das, Arindam Maitra, Sreedhar Chinnaswamy, Nidhan K. Biswas, Ajay Parida, Sunil K Raghav, Punit Prasad, Apurva Sarin, Satyajit Mayor, Uma Ramakrishnan, Dasaradhi Palakodeti, Aswin Sai Narain Seshasayee, Kumarasamy Thangaraj, Murali Dharan Bashyam, Ashwin Dalal, Manoj Kumar Bhat, Yogesh S. Shouche, Ajay D. Pillai, Priya Abraham, Varsha Potdar, Sarah Cherian, Anita Desai, Chitra Pattabiraman, M. V. Manjunatha, Reeta S. Mani, Gautam Arunachal Udupi, Vinay Kumar Nandicoori, Karthik Bharadwaj Tallapaka, Divya Tej Sowpati, Sujit Singh, Partha Rakshit, Anurag Agrawal, Christopher J. R. Illingworth, Ravindra K. Gupta
Abstract
Breakthrough infections with SARS-CoV-2 Delta variant have been reported in doubly-vaccinated recipients and as re-infections. Studies of viral spread within hospital settings have highlighted the potential for transmission between doubly-vaccinated patients and health care workers and have highlighted the benefits of high-grade respiratory protection for health care workers. However the extent to which vaccination is preventative of viral spread in health care settings is less well studied. Here, we analysed data from 118 vaccinated health care workers (HCW) across two hospitals in India, constructing two probable transmission networks involving six HCWs in Hospital A and eight HCWs in Hospital B from epidemiological and virus genome sequence data, using a suite of computational approaches. A maximum likelihood reconstruction of transmission involving known cases of infection suggests a high probability that doubly vaccinated HCWs transmitted SARS-CoV-2 between each other and highlights potential cases of virus transmission between individuals who had received two doses of vaccine. Our findings show firstly that vaccination may reduce rates of transmission, supporting the need for ongoing infection control measures even in highly vaccinated populations, and secondly we have described a novel approach to identifying transmissions that is scalable and rapid, without the need for an infection control infrastructure.