(CNN) The offer seemed too good to refuse: "Come and take the coronavirus vaccine and get 750 rupees."
Residents of the slum areas of the central Indian city of Bhopal, who recalled hearing about the offer back in December, said they scrambled to take it up. 750 rupees ($10) is about twice what they'd usually earn for a day's hard labor.
"They told us it is the corona vaccine and we should get it so that we don't fall sick," said Yashoda Bai Yadav, a housewife from Bhopal who participated in the trial alongside her husband.
But they say they later discovered from local activists that some of them hadn't been given an approved vaccine. Instead, they had unwittingly taken part in a clinical trial for India's homegrown vaccine, Covaxin. Only half of the participants in Covaxin's Phase 3 trial received a vaccine -- the other half received a placebo, a normal part of clinical trials.
One participant, Radha Aherwar, only found out it was possible she got a placebo while speaking to CNN, saying, "Oh, so what I got wasn't a vaccine? I didn't know that there was a possibility you could get a water shot."
Their experience suggests the medical team from People's Hospital, which was running the trial, may have failed to adequately explain that they were part of a trial and that only some of the participants would receive a vaccine. Both alleged lapses, if proven true, appear to violate India's clinical trial rules that require informed consent from all participants.
The study was sponsored by the vaccine's developers, Indian biotech company Bharat Biotech and the Indian Council of Medical Research (ICMR). Bharat Biotech, ICMR and People's Hospital have all denied wrongdoing.
It also raises questions about the quality of data in the trial. Experts such as Amar Jesani, the editor of the Indian Journal of Medical Ethics, worry that this could lead to vaccine hesitancy among some groups in India.
Q: I'm pregnant. Should I get the Covid-19 vaccine?
A: We asked CNN Medical Analyst Dr. Leana Wen for her advice. Wen is not only an emergency physician and public health expert; she's also a mother to a 3-year-old son and a 10-month-old girl who was born during the pandemic.
Here's what she said: "Based on what we know of the vaccine, there is no reason to believe that it will have a detrimental effect on the pregnancy or the long-term health of either the mother or baby. Lack of evidence doesn't mean it can't exist, but this kind of theoretical very low risk needs to be weighed against the real and potentially very high risk of a severe outcome from Covid-19."
Read Wen's full guidance here.
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Its authorization could help speed up the vaccination rollout across the country. President Joe Biden on Thursday commemorated 50 million Covid-19 vaccine doses administered since he took office, using it as a measuring stick against his promise to put 100 million shots in people's arms in his first 100 days. But he also warned there's "a long way to go" before life will return to normal.
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Heading to the gym? Wear a mask.
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"Frankly, when the United States provides resources and gets out of the way, the Cherokee Nation does a wonderful job of delivering health care." -- Cherokee Nation Principal Chief Chuck Hoskin, Jr.
Covid-19 has disproportionately hit Native American communities, but when it comes to vaccine distribution, tribal health providers are actually outpacing many states. CNN's Harmeet Kaur speaks with Cherokee Nation Principal Chief Chuck Hoskin, Jr. about his tribe's vaccine success. Listen now.