THE PROTECTIVE EFFECT OF CONDOMS AND NONOXYNOL-9 AGAINST HIV-INFECTION

Objectives. Whether or not spermicides can reduce the risk of human im munodeficiency virus (HIV) transmission remains an important question for the control of heterosexual HIV transmission. The authors provide estimates from a reanalysis of one of the few observational studies on the efficacy of condoms and spermicides, used separately and together , per vaginal contact. Methods. In this reanalysis, three different mo dels were used to assess the efficacy of spermicides and condoms: line ar (Pearl index), exponential (maximum likelihood), and monotonic (mar ginal likelihood). Results. Reported use of barrier methods among 2743 2 contacts was as follows: condoms plus nonoxynol-9, 39%; condoms alon e, 25%; nonoxynol-9 alone, 24%; and unprotected, 11%. Under all three models, the results indicate a strong protective effect for spermicida l suppositories. The Pearl index indicated that spermicide alone is ap parently efficacious, but the efficacy per contact cannot be quantifie d with this approach. Maximum likelihood estimates for the efficacy of nonoxynol-9 alone and condoms (with or without nonoxynol-9) were 100% (95% confidence interval [CI95] = 43%, 100%) and 92% (95% CI95 = 79%, 100%), respectively. Conclusions. The data from this observational st udy suggest that spermicides may be efficacious in reducing the risk o f HIV transmission.