Selina, not her real name, blocks out the difficult parts of her life. She claims, for example, that she cannot recall the first time she had sex for money. But she revels in the scraps of good fortune that come her way, such as the fact that she never got HIV. Like Joyce, she had been in Plummer’s original 1985 cohort, and like Joyce she didn’t get infected. She bragged that she was immune. But today, when asked if she used to think she was invulnerable to the virus, she answers in a non sequitur, saying that she has to be careful because some men remove their condoms “in a tricky way.”
The life of prostitutes in Pumwani is hard. When they contract HIV, they progress to full-blown AIDS in an average of just four years — far less time than Kenyan women who aren’t sex workers, not to mention First World women. The prostitutes, says Plummer, live “incredibly violent” lives. In 1996, Selina was raped repeatedly. At that point she had tested HIV-negative for 11 years. But shortly after the rape, she tested positive. She has already suffered a variety of AIDS-related illnesses and lost more than 10 percent of her body weight. The veins on her forearms are prominent, running like long ridges down the smooth landscape of her skin. Yet Selina has staunchly refused to be told the results of her test. Kimani explains, “She can’t come to terms with the fact that she thought she couldn’t get HIV and now she has.”
There are a few others like Selina — multiply exposed, persistently negative women who suddenly have become positive. Plummer and Kimani think that in Selina’s case, the stress of the rape might have weakened her immune system. But the other women who have belatedly turned positive seem to have another risk factor: stopping prostitution.
High levels of killer T-cells are not normally maintained for long periods. They arise in response to an invading microbe, then subside. So perhaps what’s keeping the women immune is constant, low-level exposure to HIV from their johns. When the women take a vacation, their killer T-cells wane, leaving them vulnerable to the virus.
What does this mean for a vaccine? “It’s not good news,” says Plummer. After all, one would hope that immunity lasted forever, or at least for many years. If frequent booster shots are required, a vaccine would be unaffordable where it’s needed most: in the developing world.
But McMichael has a different take on the newly infected women. Kimani found that resistance runs in families, suggesting a genetic trait. Such traits have been found in other people; some Caucasians, for example, have a mutation which makes their cells impregnable to the most common strains of HIV. But the fact that the Pumwani women can get infected is actually “good news,” says McMichael. “Not for those women, of course, but it is good news for a vaccine because it means they don’t have some special, undetected genetic immunity that a vaccine couldn’t induce.”