Prevention of HIV infection. I. Assessing the effectiveness of barrier methods for HIV prevention
Wittkowski, K.M.
Aids-Forschung Aifo 4(1): 3-8
1989
ISSN/ISBN: 0179-3098 PMID: 12342795 Document Number: 369420
Both sexual abstinence and lifelong commitment to a single partner are effective countermeasures against human immunodeficiency virus (HIV) infection. The experience of several thousand years, however, shows that these methods have relatively low compliance. The strategy of selecting a partner from a population with low HIV prevalence is also weak because it depends upon the credibility of the partner. A large part of the population would accept the following strategy: within a continuing relationship between partners who have not had risky contacts in the past and whose relationship has survived a 3-6 month test, there is no danger of infection and thus no need for HIV prophylaxis. The success of this strategy depends upon 2 factors: the reliability of the prophylaxis and the compliance of both partners with the prophylaxis methods. Probability theory makes it possible to calculate the effectiveness of barrier methods under various assumptions of sexual behavior and to convert an observed Pearl index pertaining to a given barrier method, for example, condom plus nonoxynol-9, into an HIV risk per contact. For a Pearl index = 5, for example, and reasonable assumptions about the underlying statistics of fertility, 99% compliance givers .3% and 1.5% risk/contact for 100 and for 50 contacts/year, respectively; and for 100% compliance, 1.3% and 2.5%. The more frequently barrier methods are used, the less the probability of an infection, but unless compliance is nearly perfect the barrier effectiveness scarcely plays a role.