Reflecting some of the hesitancy of some people in the United States, residents of a slum in Bhopal, India were told they were getting a coronavirus vaccine, but they were actually part of a Phase-3 trial of an unproven vaccine, CNN reports.

A white van pulled into the Shankar Nagar neighborhood in the central Indian city last December with a loudspeaker blaring that people could get vaccines and a 750 rupee (roughly $10) incentive.  Dozens of people lined up at its various stops, until the van ran out of doses.

Most thought that they were getting one of the vaccine produced by Pfizer or AstraZeneca–the only two approved by any governments at the time–but they were actually getting a dose of Covaxin, a drug under development by an Indian pharmaceutical company, Bharat Biotech.  Some even got placebos without their knowledge or consent.

The neighborhood has been the subject of other medical trials, largely due to the fact that it is less than 2.5 miles from the site of one of the deadliest industrial accidents in world history:  the 1984 Union Carbide explosion, that killed nearly 4,000 people.  Many of the people in the neighborhood survived that accident and still have lingering effects from the chemical exposure.

The main clinical trial involves more than 20,000 people, run by the Indian Council of Medical Research and Bhopal’s People’s Hospital.  The drug is not expected to be approved until next year, according to government regulators, but the Indian government has already purchased more than five million doses for emergency use.