Leaving her tin-roofed brothel for the day, the 42-year-old prostitute journeys to the capital for an injection that might save not only her life, but possibly millions more around the world. Jacinta Julia Adams Fernandez, a mother of three, is one of 175 Dominican prostitutes lending their bodies to a trial of what New Jersey-based Merck & Co. hopes will prove to be a vaccine against the virus that causes AIDS. Since turning to prostitution after a divorce 13 years ago, Adams has seen friends and co-workers die from the disease. Prostitution is illegal but widespread here, largely ignored by the authorities. “It’s rare for anyone who lives here not to know AIDS and what it can do,” said Adams, a heavyset woman dressed for work in a tight-fitting yellow dress and bright red lipstick. AIDS is the leading killer of people aged 15 to 44 in the Caribbean, claiming 24,000 lives in 2005, a rate second only to that of sub-Saharan Africa. And according to the United Nations, nearly three-quarters of those infected live on the island of Hispaniola, which the Dominican Republic shares with Haiti. At least 70,000 of the Dominican Republic’s 9 million people are HIV positive, and discrimination discourages many from seeking testing or treatment. Among prostitutes, about 3.6 percent are infected, although researchers report rates as high as 12 percent in some areas. The prostitutes, who will spend much of the next four years traveling to Santo Domingo for injections and checkups, were recruited from brothels across the country. They are among some 3,000 people in eight countries testing the experimental vaccine â€” a combination of deactivated cold viruses and synthetically produced HIV genes meant to train the body to destroy infected cells. Any long-term risks will take years to discover, but once doctors explained there was no way to contract the disease from the vaccine, they found plenty of volunteers at Adams’ brothel in Las Guaranas, a town of dirt streets and low-slung houses surrounded by rice fields about 75 miles north of Santo Domingo. Many were turned away because of pregnancy, conditions like high blood pressure or because they are already infected. Participants don’t know whether they are getting the drug or a placebo. Even if the results are promising, a vaccine would be several years away from reaching the market. The program pays the women’s meals, transportation and $30 for a lost day’s work. A handful have dropped out, and the clinic provides health training and occasional gifts like bags of cosmetics to keep others from losing interest. Participants get three injections over their first seven months in the study, and then must keep reporting back for four years of close monitoring. For many, the greatest reward is pride. “We are doing it for the world,” said 38-year-old Lucila Mendoza Ovalle. The other test sites â€” Haiti, United States, Australia, Brazil, Canada, Jamaica and Peru â€” all have the same strain of HIV, said Merck spokeswoman Janet Skidmore. The strain is also found in Europe, meaning a formula that works here could find a lucrative global market. A trial was launched Thursday in South Africa to see if the vaccine would have any effect on African strains. The Merck trial, currently in the second of three testing phases â€” each of which is to last several years â€” is one of 17 sponsored by the HIV Vaccine Trial Network, a Seattle-based group supported by the U.S. government. The trial is “is an extremely important step, but not the only one,” said Dr. Jorge Flores, chief of vaccine research for the AIDS division at the U.S. National Institute of Allergy and Infectious Diseases. He stressed the importance of education and research into other strategies, like microbicides in vaginal gels. Even a vaccine that reduces the level of HIV in future infections would be a victory. “A 90 percent, 80 percent reduction is going to be acceptable for the time being,” said Dr. Ellen Koenig, who heads one of two Santo Domingo clinics testing the formula. Margarita Ramirez de los Santos, 24, said she volunteered after her brother and sister-in-law died of AIDS. “I am worried about my health,” she said. Meanwhile, Adams’ brothel insists on more familiar methods â€” condoms and frequent testing for HIV. And if a client refuses to use protection? “We kick him out,” Adams says with a laugh.