Treatment as Prevention – A Three Part Series

Part Two – Controversy Rocks Foundations of Prevention Messaging
Community Response to the Controversial Swiss Study

The mantra of AIDS Service Organizations for the last twenty years has been that the best way to prevent the transmission of HIV is to use a condom, properly, every time you engage in sexual activity. But the recent statement made by the Swiss Federal Commission for HIV/AIDS in their Bulletin of Swiss Medicine is posing a challenge to this fundamental message (see Part 1 – HIV Treatment Debate Rages).

The statement suggests that people living with HIV who are on antiretroviral treatment and have undetectable viral loads do not pose a risk of sexual transmission to their partners. The community has responded with a resounding cry for proof, assailing the Commission’s statement and admonishing them for publishing a document based on “opinion” and “belief” rather than fact. Interestingly, even the Commission is reluctant to make any firm guarantees in relation to their statement.

As they explain, “medical and biologic data available today do not permit proof that HIV-infection during effective antiretroviral therapy is impossible, because the non-occurrence of an improbable event cannot be proven. If no transmission events were observed among 100 couples followed for two years, for instance, there might still be some such events if 10,000 couples are followed for ten years. The situation is analogous to 1986, when the statement ‘HIV cannot be transmitted by kissing’ was publicised. This statement has not been proven, but after 20 years’ experience its accuracy appears highly plausible.” 1

In many ways, this parallel pinpoints the grey areas within which public health officials and AIDS Service Organizations have operated for the past 30 years. In truth, when it comes to HIV transmission, it is almost impossible to prove anything beyond a level of uncertainty. Ethically speaking, scientists cannot run controlled studies on human subjects while knowingly placing them at risk of HIV transmission. In the absence of hard scientific evidence, the community is forced to operate within a realm of estimations, based on the best scientific data available, but often without totally definitive scientific proof. In other words, recommendations get made, and everyone crosses their fingers and hopes that they are right.

In the case of the Commission’s statement, there seems to be a general consensus that the risks are too high to just cross our fingers and hope for the best, and the evidence is not strong enough to inspire confidence.

Significantly, a recent study by UNSW's National Centre in HIV Epidemiology and Clinical Research (NCHECR) found that if the Swiss Commission’s statement were adopted at the community level, over a ten year period HIV transmission among serodiscordant couples would be four times higher in couples who abandon condom use than if condoms had been used. The study used mathematical modeling to extrapolate HIV transmission in a population of 10,000 serodiscordant couples and showed that there would be 215 female-to-male transmissions, 425 male-to-female transmissions and 3,524 male-to-male transmissions. As Dr. Wilson, one of the study authors states, "While it is true that the individual risk of HIV transmission per act is fairly small for people on antiretrovirals, the risk of transmission over large numbers of acts could be substantial.” 2

It is within this context that we must view the statements put forward by the Swiss Commission. The best way to reduce HIV transmission remains to use a condom properly every time you engage in sexual activity. For people living with HIV/AIDS, being adherent to your HIV treatment, maintaining an undetectable viral load, testing for and treatment of all STIs are all additional ways to reduce the risk of passing HIV to your partner. Practicing these steps, in conjunction with regular and consistent condom use, provides a new strategy for reducing risks even further. In many ways, this is great news for serodiscordant couples as it provides new tools and peace of mind for preventing the onward transmission of the virus, and poses a great incentive to stay adherent to one’s treatment and improve one’s overall health.

Part Three of Treatment as Prevention

1 Bernard, Edwin J. (2008). Swiss experts say individuals with undetectable viral load and no STI cannot transmit HIV during sex. http://www.aidsmap.com/en/news/4E9D555B-18FB-4D56-B912-2C28AFCCD36B.asp Retrieved November 2008

2 Study Says Swiss Commission Advice may See HIV Infection Quadrupling http://www.medindia.net/news/Study-Says-Swiss-Commission-Advice-may-See-HIV-Infection-Quadrupling-40023-1.htm Retrieved November 2008.