California Partner’s Study

NOTE: This study has ended.



Heterosexual transmission of HIV has become the leading route of infection for women in the US, and is steadily increasing among heterosexual men. Interventions targeted at heterosexuals are sparse, primarily target women, and are rarely evaluated. Also, there is a lack of HIV services for couples, specially outside of SF. In the California Partner’s Study II (CPS II), we want to understand how people in relationships make decisions about risk, how they decide to make changes and how we can best help them through the process.

CPS II follows California Partners Study I (CPS I), a 10-year study based in Northern California that looked at sexual transmission of HIV between men and women. This study was unique in that we observed no new infections over greater than 3300 couple-months of follow-up.

CPS II will evaluate the effectiveness of a brief intensive intervention for HIV-serodiscordant heterosexual couples (where one partner is HIV+ and the other is HIV-). We will also attempt to identify virological or immunological factors associated with prevention of transmission as studied in women who are exposed to HIV, but who remain uninfected.


CPS II compares the benefits of providing intensive risk reduction counseling to the HIV+ partner only versus providing intensive risk reduction counseling to each partner in the couple. The program follows participants for one year, conducting 3 surveys with collection of blood and urine: at baseline, 6 months and 12 months.

After the baseline visit, couples are randomized into either a couple’s intervention where each partner receives intensive one-on-one HIV-risk reduction counseling, or an individual intervention which includes intensive counseling only for the HIV+ partner, and support and referrals to the HIV- partner.

Qualitative Study

A subset of couples who completed the study were to participate in a follow-up in-depth interview as part of our qualitative sub-study. The qualitative interview focused on services and support received including experience with the study intervention; concerns about and access to new treatments for HIV and risk management in the relationship.

Biological Study

We also conducted a biological sub-study with some of the couples. The biological study worked with three different kinds of couples and studied differences in semen, genital mucus and blood. This study wroked with couples where the woman was exposed to HIV and remained unifected and compared them to two other types of couples: 1) concordant seropositive couples where transmission occurred between the man and woman, and 2) known concordant seronegative couples where neither man nor woman was ever exposed to HIV.

Findings about couples

CPS II believes it is important to work with couples for several reasons. When people are in a relationship, HIV affects BOTH partners in the relationship. No one takes HIV risks alone. People at risk are having sex and sharing needles with other people (often their partners). And both partners will influence decisions about risk and safety in the relationship. Also, relationship concerns may compete with concerns about HIV transmission.

During focus groups conducted with participants from the first 10 year study, CPS I, we discovered four key areas important to managing HIV in serodiscordant couples:

  • Communicating about HIV
  • Keeping sex alive
  • Involving/engaging the male partner
  • Providing support and counseling to the HIV- partner

A full report can be found in the article: “Managing HIV among serodiscordant heterosexual couples: serostatus, stigma and sex.” van der Straten A; Vernon KA; Knight KR; Gomez CA; Padian NS. AIDS Care, 1998 Oct, 10(5):533-48.


CPS II worked with agencies and participants in their own communities. We are no longer recruiting for this study. For more information about how we recruited, please see our recruitment sheet.


During the full implementation phase of the study , there were 15 staff on the CPS II including recruiters, counselors, interviewers, researchers, clinicians and administrative personnel. CPS II staff speak both English and Spanish. Meet the CPS II staff.

Last modified: October 22, 2012