Yet money is not the only factor in the equation, Lamberti says, whose work includes helping pharmaceutical companies find suitable locations for clinical trials. It's easier and takes far less time to find suitable subjects in many developing countries, she says, because they have large "drug naive" populations.
In other words, a large percentage of Americans are already on various medications, so it's difficult to find subjects with unadulterated -- that is, completely unmedicated -- bodies in the United States.
Critics say there is an additional issue that has yet to be taken seriously.
Individual countries generally have their own boards of medical professionals charged with setting standards to ensure the safety of their citizens. And the United States, for example, has an arm of the Food and Drug Administration tasked with overseeing clinical studies performed abroad. The trouble, critics say, is that the standards that exist are sometimes not upheld.
Sonia Shah, author of the 2006 book "The Body Hunters: Testing Drugs on the World's Poorest Patients," tells ABCNews.com that there is a "whole steamrolling industry that needs more and more subjects."
She adds, "[The] political will is not there" to protect the interests of those who put their bodies at risk.
Pneumococcal diseases -- that is, diseases caused by bacteria that cause pneumonia, middle ear infections, meningitis and blood infections -- are a serious problem in Latin America. According to international health organizations, each year more than 50,000 children die from them.
Dr. Ricardo Ruttiman, the regional medical affairs and research and development director of GlaxoSmithKline responsible for Protocol Compas in Argentina, says the study is being conducted in three Argentine provinces -- Santiago, Mendoza and San Juan. Ruttiman says Compas clinical studies began a little more than a year ago.
Twelve Argentine children who participated in Protocol Compas have died, and of those 12, seven are being mourned in Santiago del Estero, one of Argentina's poorest provinces. Like Ester, many of the parents reportedly blame what they know as Protocol Compas, or simply, Compas.
"Within the COMPAS trial an Independent Data Monitoring Committee (IDMC) oversees safety aspects of the study and ensure that the highest ethical and compliance standards are followed," said Sarah Alspach, director of US Media Relations for GlaxoSmithKline. "The mortality rate of children participating in the COMPAS study is closely monitored by the IDMC and does not exceed the rate in the regions and countries participating in the study."
Some parents say they didn't know that their children were participating in a study at all. Others claim to have been coerced into participating -- a suggestion rebutted by Ruttiman, who told ABCNews.com that participation is always voluntary and that parents "are informed, clearly and in a language they can understand, by experienced medical investigators."
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.