In the second of six papers in The Lancet Series on HIV prevention, researchers call for HIV prevention efforts to focus on proven biomedical methods. As we have yet to develop an HIV vaccine, core preventions methods such as male condoms, male circumcision, and prophylactic antiretroviral (ARV) drugs (that prevent mother-to-child transmission) should be emphasized. These recommendations come amidst promising results that have been demonstrated with people who use oral and vaginal ARVs for both pre-exposure prophylaxis and to reduce post-exposure infectiousness.
Dr Nancy Padian (Women’s Global Health Imperative, RTI International, San Francisco, CA, USA), Dr Ward Cates (Family Health International, North Carolina, USA) and colleagues maintain that infected individuals should be targeted for prophylactic treatment, just as with other sexually transmitted infections (STIs). If the treatments are effective, there can be a scale-up after resistance and distribution issues are resolved. Though the female diaphragm with male condom use has not resulted in extra protection compared with male condom use alone, there are new female condom designs in trial phase that are designed to improve uptake. Studies show that the female condom is as effective as the male condom at preventing transmission of HIV. If an antimicrobial gel called BufferGel proves safe and effective against HIV, it will be joined with a disposable, one-size-fits-all, clear diaphragm resulting in a potentially effective barrier to HIV transmission.
An important consideration in preventing HIV infection is controlling other STIs, which usually facilitate HIV transmission. For example, HIV prevention is weakened by concurrent infection with STIs such as the genital ulcerative diseases syphilis and herpes (herpes simplex virus-2/HSV2). There has not been much success in preventing HIV by treating herpes infections, and even if there were, the authors note that, “Introduction of such interventions at a population level is probably not feasible, especially since the prevalence of HSV-2 infection is high in many low-resource settings.”
A second biomedical strategy that has reduced risk of HIV transmission by 58% is male circumcision (MC). Although studies have shown that some men think they are safer after MC and engage in risky behaviors, others do not. In addition, men must wait for their wounds to heal before engaging in sexual activity. One study has shown, however, that MC did not offer female partners protection from HIV infection. MC has been cited as a cost-effective preventive measure – the one-time-only procedure could cost about US$47 per circumcision and could offer a US$181 cost per HIV infection averted, according to study estimates from the Gauteng Province, South Africa. “A 100% uptake of MC could avert an estimated 2 million deaths during 10 years in sub-Saharan Africa and 5.7 million infections during 20 years,” write the authors.
A third effective biomedical strategy that requires scale-up is ARV treatment to prevent mother-to-baby transmission. The researchers also suggest that an effective HIV prevention technique may lie in contraception for HIV-positive women who do not wish to become pregnant. For all interventions, researchers should focus on the measurement and improvement of adherence. Though the authors note that it is highly unlikely a vaccine will be available for many years, phase III trials of candidate vaccines and also microbicides are still being conducted because, “We simply do not know what does and does not work, and additionally we will learn valuable lessons from the trials, which we have.”
It will be a combination prevention package of partially effective interventions targeted to specific individuals, not a single solution, that will result in successful prevention outcomes. The researchers conclude that, “As we approach the era of antiretroviral-based prevention (alone or as part of a combined package) to reduce HIV acquisition in uninfected individuals and to decrease HIV infectiousness in infected individuals, we should exercise restraint and not again set standards so high that moderate-level prevention strategies, which could offer measurable individual and population benefits, are destined not to demonstrate efficacy.”
Biomedical interventions to prevent HIV: Evidence, challenges and the way forward
Nancy Padian et al.
The Lancet (2008).
Written by: Peter M Crosta