Prevalência e vulnerabilidade à infec？？o pelo HIV de moradores de rua em S？o Paulo, SP

objective: to assess the prevalence and vulnerability of homeless people to hiv infection. methods: cross-sectional study conducted with a non-probabilistic sample of 1,405 homeless users of shelters in the city of s？o 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. results: 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. conclusions: the hiv epidemic has a major impact on homeless people reflecting a cycle of exclusion, social vulnerability, and limited access to prevention.