Transmission of B.1.617.2 Delta Variant between vaccinated healthcare workers

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 fully vaccinated individuals (two doses) to transmit SARS-CoV-2 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 using a suite of computational approaches. 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.