They are informed not only about the benefits, he says, such as round-the-clock access to medical care and vaccinations against diseases such as diphtheria, tetanus and hepatitis, but about potential risks.
Ruttiman says there are few risks. The safety of the drug has already been proved, he says, and the vaccine's efficacy against respiratory infections is only being tested.
He adds that "the vaccines used in this study may cause adverse reactions unknown up to now. … As with any vaccine, unexpected adverse events can arise, including allergic reactions."
Ester, who earns a living cleaning houses, says Michaela is among those who experienced an "adverse event."
Three weeks before Christmas, a nurse's aide came to the Esters' home. The nurse's aide, says Ester, who spoke to ABCNews.com through a translator, told her that doctors at the Eva Peron Children's Hospital, Santiago Del Estero's primary children's hospital, wanted to give Michaela a vaccine.
Ester -- who told her story to ABCNews.com and a small audience that included five neighborhood children sitting as quietly as possible on the pungent bed -- says that a friend had warned her to stay away from Protocol Compas. The friend told Ester that she knew of another new mother whose baby reportedly suffered health problems after participating in the study, according to Ester.
Ester only gave in, she says, when the nurse's aide threatened to go to the police and have her baby taken away from her. "I didn't know if the doctors, the police, the system would take her away, but I was afraid," she added.
Ester soon signed a 12-page consent form she says she couldn't really understand. Then she allowed Michaela to receive her first injection.
Many health-care professionals assert that holding clinical trials in regions with poor health-care systems has the potential to benefit everyone. GSK's Ruttiman points out that because of the high quality of care the children in the study receive, the infant mortality rate is significantly lower in those who participate in Protocol Compas than in those who do not. Ruttiman would not comment on individual cases citing patient privacy.
Benjamin Wilfond, head of Seattle's Treuman Katz Center for Pediatric Bioethics, says that although he is unfamiliar with Protocol Compas, it's difficult to know what really happened between Ester and the nurse's aide.
"I have no doubt that that was how [Ester] experienced the process. And you will not find anyone who will defend coercion," he said. "But I was in Argentina a few years ago, and the internal regulations seemed quite robust. It could very well be true, because even if the process is being appropriately reviewed, it's difficult to monitor what goes on [on] the ground, what individuals take it upon themselves to do. But I would be wary [of such accounts]. The death of a child could be processed in all sorts of ways. It could very well be true. But I am skeptical."
Trading participation in a medical trial for health care has become the standard operating procedure for drug companies and/or their medical contractors, according to Shah. Some see it as win-win, but Shah views the trade as nearly as coercive as the dramatic threat Ester alleges she received.