Risk of COVID-19 infection among frontline healthcare workers during the COVID-19 pandemic

Figure 1 The timeline of the study. T1 to T5 reflects the five time points when sampling was done for the seroprevalence study. The first coronavirus disease 2019 (COVID-19) case was reported in India on 27^th January 2020. The index case of COVID-19 was reported in our institution on 28^th March 2020 while the first confirmed COVID-19 infection in a healthcare worker (HCW) was reported on 5^th July 2020. The period T1 to T3 denotes the first wave of the pandemic during which time vaccine was not available. Vaccination for COVID-19 started in India for HCWs on January 16^th, 2021. T4 and T5 denote the period when vaccination was rolled out in a phased manner and also reflects the period when the second wave of the pandemic occurred in India. COVID-19: Coronavirus disease 2019; HCW: Healthcare worker.