Microbicides: Issues around partial effectiveness

1. Microbicides:Issues around partial effectiveness Lori Heise, Director EATG/GCM Training December 9, 2005

2. Confronting partial effectiveness • Concern has been raised about introducing a method that is less efficacious than condoms • Will individuals default from condoms to microbicides because they are easier to use (“condom migration”)? • What should our counseling messages be?

3. Shift to a “harm reduction approach” • Microbicides will be promoted as an adjunct and/or back-up to condoms, not as an alternative • Prevention messages would shift to a hierarchy of options: • Use a male or female condom every time you have sex; if you absolutely can’t use a condom, use a microbicide • Use a microbicide with your condom for added pleasure and protection

4. A Balancing Act to Minimize HIV Risk condoms Up to 90%efficacy ? consistency of use microbicides 40-60% efficacy ?consistencyof use

5. The Prevention Equation • Level of protection conferred (the number of cases averted) depends on the product of three factors: • Efficacy of the method • Consistency of use within a partnership • Extent of use in a sub-population

6. The Prevention “Trade-Off” • A 90% efficacious method (like condoms) used in 20% of sex acts, provides less protection than a: • 70% efficacy used> 30% of the time • 50% efficacy used> 40% of the time • 30% efficacy used> 60% of the time

7. What do we know about likely use? • Multiple studies document widespread interest • 15 country qualitative study by ICRW • 2 market studies: one global and one US • In clinical trials and acceptability studies where women have experience using products, they articulate clear advantages to microbicides: • Easier to use than condoms • Allows skin on skin intimacy • Woman initiated

8. Acceptability & Use Dynamics • Covert use early emphasis of microbicide field • Recent research suggests that most women would tell their partner • some women afraid to risk • others want partners involved • “Passive acquiescence” versus “active involvement” • Can be “negotiated” once rather than at every act of intercourse • No need to talk about sex • Allows skin to skin intimacy • Can enhance pleasure

9. Condom migration: should we be concerned?

10. More protection or less? • Three lines of evidence suggest that introducing microbicides will lead to more protection rather than less • experience from family planning • data from intervention studies • insights from modeling

11. LSHTM Modeling Studies • Under most circumstances, substantial migration can be tolerated without increasing risk of infection • either at the level of individuals • or among sub-populations • Migration is potentially a problem only where condom use is high (>70%) and microbicide consistency is low (<50% of non-condom protected acts)

12. Reductions in condom consistency that an individual can tolerate without increasing her risk Microbicide HIV/STI efficacy = 50%; Used in 50% of acts not protected by condoms Condom Consistency Condom Consistency BEFOREAFTER 30% 5% 50% 32% 70% 59% 90% 86%

13. Reductions in condom consistency that could be tolerated without increasing risk Microbicide HIV/STI efficacy = 50%; Used in 100%of acts not protected by condoms Condom Consistency Condom Consistency BEFOREAFTER 30% 0% 50% 0% 70% 37% 90% 79%