The variant may have led to insufficient neutralising immunity in people, despite high seropositivity, and social behaviour may have augmented the surge by promoting transmission, they added.Neutralising immunity consists of naturally occurring antibodies that play an important role in the immune system.To determine whether SARS-CoV2 variants may be responsible for the April 2021 outbreak in Delhi, the researchers sequenced and analysed community samples from Delhi from the previous outbreak in November 2020 until May 2021 and related it to effective reproductive number (Rt).The effective reproductive number is the expected number of new infections caused by an infectious individual in a population where some individuals may no longer be.