Patients at Nkosi's Haven, south of Johannesburg, South Africa, Nov. 28, 2014. Nkosi's Haven provides residential care for destitute HIV-positive mothers and their children, whether HIV-positive or not. Reuters

Researchers on the front lines of HIV/AIDS eradication have often operated on shoestring budgets and faced an ever-evolving enemy, but perhaps the greatest obstacle to ending the pandemic that has killed an estimated 39 million people in three decades has been stigma. In some areas of sub-Saharan Africa, where the vast majority of new infections have occurred, shame has kept many at-risk people from seeking treatment or taking measures to prevent infection, especially among women, who account for the majority of new HIV infections on the continent.

When presented with state-of-the-art drugs that have proved to be powerful, safe and effective at preventing HIV infection, many women were reluctant to take the medications or stopped taking them altogether, according to a study published Wednesday in the New England Journal of Medicine that looked at the rates of HIV infection among women in sub-Saharan Africa. “We get to the end, and we find on average that 28 percent of women were using” the medications, Jeanne Marrazzo, a professor of medicine at the University of Washington in Seattle and co-author of the study, told International Business Times. “We were quite disappointed.” The trial was conducted between September 2009 and August 2012.

One of the best defenses in recent years in the fight against HIV/AIDS has been pre-exposure prophylaxis, or PrEP, treatments – antiretroviral drugs used preventively to lower the risk of an HIV-negative person from getting infected, something health experts have described as being like wearing a seat belt while driving. Despite what researchers said were their best efforts to explain the benefits of PrEP to women involved in the study, only a small portion of participants continued the treatments all the way through.

During the trial period, researchers surveyed more than 5,000 women, the majority of whom lived in South Africa. Participants were given one of three PrEP treatments – Truvada, tenofovir or tenofovir vaginal gel – in addition to a placebo group. Truvada was approved by the U.S. Food and Drug Administration in 2012 and has been shown to reduce HIV risk by up to 92 percent in people who take it preventively.

Study participants were asked to report their use habits throughout the trial, and the majority seemed on course. Blood samples, however, ultimately showed that most of the women had stopped treatment. “We asked them, ‘What happened here?’ ” Marrazzo said.

The answers researchers got were not what they expected, she said. “They were really about the concern over having an anti-HIV drug in their bodies and households,” Marrazzo explained. “There was a huge amount of stigma and shame that ... as researchers, I don’t think we appreciate. It was very concerning for them that their boyfriends, their sisters, their mothers might think they had HIV” should they stumble upon the women’s medications or empty bottles lying around their homes.

Marrazzo and her colleagues concluded that based on the women’s unwillingness to participate in the study, none of the three products tested was effective at preventing new cases of HIV. Of the 5,007 participants, 312 women, or 6 percent, contracted HIV during the study, the authors noted.

By many accounts, the world has reached the beginning of the end of the HIV/AIDS pandemic. Antiretroviral drugs have advanced tremendously. The infection rate has stabilized. The number of AIDS-related deaths has declined. More people than ever received life-saving antiretroviral medicines in 2012, according to UNAIDS. There’s even a vaccine in the works that has shown tremendous potential for protecting against HIV. Optimism is at an all-time high – the United Nations has set a goal of ending the HIV/AIDS pandemic by 2030.

However, there’s still no cure for HIV/AIDS, and antiretroviral drugs only work when used. Globally there were 35 million people living with HIV in 2013, according to the World Health Organization. That year, there were 2.1 million new cases of HIV around the world, 68 percent of which occurred in sub-Saharan Africa.

Sometimes, when racing against the clock, the final seconds can stretch on the longest. “We have a lot in our tool belt right now, but picking the right interventions for the right groups of people is something that we still need a lot of research in,” David Gerberry, assistant professor of mathematics at Xavier University who has modeled HIV interventions in sub-Saharan Africa, told IBTimes. “In general, you want to target your interventions at people who are the highest risk, which is hard because nobody walks around with a T-shirt saying, ‘I have an 87 percent chance of getting HIV this week.’ ”

HIV, or human immunodeficiency virus, works by weakening the body’s immune system, destroying the cells that protect the body from disease and infections. The virus is carried by bodily fluids including blood, semen and breast milk. Unlike the flu virus, the body cannot flush out HIV. When left untreated, HIV can eventually become AIDS, or acquired immunodeficiency syndrome. AIDS is the final stage of HIV infection.

Worldwide, 80 percent of new cases are through unprotected sex with an infected person, as opposed to by sharing needles or through breast milk from mother to baby. Some health experts have said that a treatment-based approach only works when other factors like behavior and cultural norms are taken into account.

“If we continue to focus on the drugs without acknowledging that we’ve only reached the 5 million out of the 25 million in Africa, then we’re really just kind of kidding ourselves,” Susan Allen, professor in the school of medicine at Emory University in Atlanta and founder of the Rwanda Zambia HIV Research Group, told IBTimes. She has advocated for a more involved approach to HIV eradication that would include counseling couples about the risks and myths of HIV. “Until every premarital couple is tested,” and couples counseling becomes more widespread, “we’re just kind of chipping away at the edges,” she said. The majority of new infections of HIV in Africa – by some estimates, between 80 percent and 90 percent – are transmitted between people in committed relationships, according to Allen.

One of the biggest problems with drug-based approaches has been adherence. Many people have dropped out of care because they haven’t been able to stick with the daily regimens. While the drugs themselves usually have been provided, patients typically have to pay for their own laboratory monitoring, or end up waiting in line at the clinic all day, “which means you’re not out earning money,” Allen said. HIV treatment becomes a financial burden that many simply cannot afford.

Developing a vaccine to prevent HIV has widely been regarded as the ultimate weapon against HIV/AIDS, but that’s still years down the road. To date, scientists have developed four vaccines against HIV, but only one offered some level of protection against the virus, according to a report by CNN.

Vaccines also take a great deal of time to develop. It took researchers 42 years to fully develop a vaccine against measles, and 47 years to reach a polio vaccine. HIV was discovered 32 years ago.

In the meantime, eradicating HIV will need to involve more than PrEP, health experts have said. “[The study was] a big wakeup call that if we want to empower these women to use biological tools, then we need to work with them to make that possible,” Marrazzo said. “We have to look at different approaches. ... It’s more than saying, ‘This product works, use it.’ ”