Transmission of B.1.617.2 Delta Variant between vaccinated healthcare workers in Delhi, India

Breakthrough infections with SARS-CoV-2 Delta variant have been reported in vaccine recipients and in individuals infected with previous variants, however the potential for doubly vaccinated individuals to transmit the virus is unclear. We here analyse data from health care workers in two hospitals in India, constructing probable transmission networks from epidemiological and virus genome sequence data. Among known cases we identify a high probability that doubly vaccinated individuals transmitted SARS-CoV-2, and potential cases of virus transmission between individuals who had received two doses of vaccine. Our findings highlight the need for ongoing infection control measures even in highly vaccinated populations.