Prevalence and vulnerability of homeless people to HIV infection in São Paulo, Brazil

To assess the prevalence and vulnerability of homeless people to HIV infection. Cross-sectional study conducted with a non-probabilistic sample of 1,405 homeless users of shelters in the city of São Paulo, southeastern Brazil, from 2006 to 2007. They were all tested for HIV and a structured questionnaire was applied. Their vulnerability to HIV was determined by the frequency of condom use: those who reported using condoms only occasionally or never were considered the most vulnerable. Multinomial and logistic regression models were used to estimate effect measures and 95% confidence intervals. There was a predominance of males (85.6%), with a mean age of 40.9 years, 72.0% had complete elementary schooling, and 71.5% were non-white. Of all respondents, 15.7% reported being homosexual or bisexual and 62,0% reported having casual sex. The mean number of sexual partners in the last 12 months was 5.4. More than half (55.7%) of the respondents reported lifetime drug use, while 25.7% reported frequent use. Sexually-transmitted disease was reported by 39.6% of the homeless and 38.3% reported always using condoms. The prevalence of HIV infection was 4.9% (17.4% also tested positive for syphilis) and about half of the respondents (55.4%) had access to prevention programs. Higher HIV prevalence was associated with younger age (18-29 years, OR = 4.0 [95%CI 1.54;10.46]); past history of sexually-transmitted disease (OR = 3.3 [95%CI 1.87;5.73]); homosexual sex (OR = 3.0 [95%CI 1.28;6.92]); and syphilis (OR = 2.4 [95%CI 1.13;4.93]). Increased vulnerability to HIV infection was associated with being female; young; homosexual sex; having few partners or a steady partner; drug and alcohol use; not having access to prevention programs and social support. The HIV epidemic has a major impact on homeless people reflecting a cycle of exclusion, social vulnerability, and limited access to prevention.