More than a dozen slum residents in an Indian city say they thought they were being vaccinated. They were part of clinical trials

The white van arrived in slum areas of Bhopal, a city in central India, blasting a message over the speaker system that seemed too good to refuse: "Come and take the coronavirus vaccine and get 750 rupees ($10)."

source https://www.cnn.com/2021/02/25/asia/india-vaccine-trials-covid-ethics-intl-dst-hnk/index.html