Objectives: Report of risk behavior, HIV incidence, and pregnancy rates among women participating in the STEP study, which is a phase IIB trial of MRKAd5 HIV-1 gag/pol/nef vaccine in HIV-negative individuals who were at high risk of HIV-1.
Design: Prospective multicenter, double-blinded, placebo-controlled trial.
Methods: Women were from North American, and from Caribbean and South America (CSA) sites. Risk behavior was collected at screening and 6-month intervals. Differences in characteristics between groups were tested with chi-square, two-sided Fisher's exact tests, and Wilcoxon rank-sum tests. Generalized estimating equation models were used to assess behavioral change.
Results: Among 1134 enrolled women, the median number of male partners was 18; 73.8% reported unprotected vaginal sex, 15.9% unprotected anal sex and 10.8% evidence of a sexually transmitted infection in the 6 months prior to baseline. With 3344 person-years of follow-up, there were 15 incident HIV infections: incidence rate was 0.45 per 100 person-years [95% confidence interval (CI) 0.25, 0.74]. Crack cocaine use in both regions [relative risk (RR) 2.4 (1.7, 3.3)] and in CSA, unprotected anal sex [RR 6.4 (3.8, 10.7)], and drug use [RR 4.1 (2.1, 8.0)] were baseline risk behaviors associated with HIV acquisition. There was a marked reduction in risk behaviors after study enrollment with some recurrence in unprotected vaginal sex. Of 963 nonsterilized women, 304 (31.6%) became pregnant.
Conclusion: Crack cocaine use and unprotected anal sex are important risk criteria to identify high-risk women for HIV-efficacy trials. Pregnancy during the trial was a common occurrence and needs to be considered in trial planning for prevention trials in women.
aSection of Infectious Diseases, Department of Medicine, University of Illinois at Chicago, Chicago, Illinois
bVaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington
cSan Francisco Department of Public Health, San Francisco, California, USA
dVIA LIBRE, Perú
eUnidad de Vacunas IDCP-COIN-DIGECITSS, Santo Domingo, Dominican Republic
fDepartment of Community Health and Psychiatry, University of the West Indies, Jamaica
gCentres GHESKIO, Port-au-Prince, Haïti
hInst. Dominicano de Estudios Virologicos, Santo Domingo, Dominican Republic
iUniversity of Pennsylvania Department of Psychiatry, Division of HIV Prevention Research, Philadelphia
jDivision of Infectious Diseases, Columbia University Medical Center, New York, New York, USA
kUniversity of Ottawa/The Ottawa Hospital, Ottawa, Ontario, Canada
lUPR School of Medicine, Maternal-Infant Studies Center (CEMI), San Juan, Puerto Rico.
Correspondence to Richard M. Novak, Professor and Head, Section of Infectious Diseases, University of Illinois at Chicago, 808 S. Wood St., M/C 735, Rm 888, Chicago, IL 60612, USA. Tel: +1 312 996 6763; fax: +1 312 413 1657; e-mail: email@example.com
Received 1 November, 2012
Revised 24 February, 2013
Accepted 1 March, 2013