What is the most effective prevention strategy for a patient with Human Immunodeficiency Virus (HIV) and an undetectable viral load, who is taking Antiretroviral Therapy (ART), to prevent transmission to their HIV-negative partner?

Most Effective HIV Prevention Strategy for Virally Suppressed Patient

For this patient with sustained viral suppression (<200 copies/mL) on ART, maintaining viral suppression by continuing ART as prescribed (Option D) is the most effective prevention strategy and eliminates sexual HIV transmission risk.

Evidence for Treatment as Prevention

The highest quality evidence demonstrates that maintaining undetectable viral load through consistent ART adherence essentially eliminates HIV transmission risk to sexual partners:

• The HPTN 052 randomized controlled trial demonstrated that ART reduced HIV transmission by 96% when combined with standard prevention strategies 1
• The PARTNER Study, a prospective observational study of 767 serodiscordant couples (40% same-sex male couples), reported zero HIV transmissions over 894 couple-years of follow-up during condomless sex when the HIV-infected partner maintained viral suppression on ART 1
• Multiple international guidelines (IAS-USA, WHO, PEPFAR) recommend ART for all HIV-infected individuals specifically because viral suppression eliminates sexual transmission risk (evidence rating AIa) 1

Critical Caveats for "Undetectable = Untransmissible" (U=U)

While this patient's strategy is optimal, important counseling points must be emphasized:

• 3-6 months of sustained viral suppression is required before transmission risk is eliminated; the few transmissions observed in studies occurred early after ART initiation 1
• Durable viral suppression cannot be assessed from a single measurement—consistent adherence and regular monitoring are essential 1
• HIV transmission risk persists during the first 6 months of ART, with residual HIV RNA detectable in genital compartments in 12-21% of samples 2

Why Other Options Are Less Effective

Option B (Condoms): While condoms are effective and recommended for preventing other STIs 1, they are less effective than maintained viral suppression for HIV prevention alone 1

Option A (On-demand PrEP for partner): On-demand PrEP is only recommended for men who have sex with men with infrequent exposures (evidence rating AIa) 1. More importantly, PrEP is specifically indicated for HIV-negative partners of HIV-infected persons who do NOT have consistent viral suppression 1. Since this patient has documented viral suppression, PrEP for the partner is unnecessary and represents overtreatment.

Option C (Post-exposure prophylaxis): PEP is for use after a specific high-risk exposure and must be started within 36-72 hours 1, 3. It is not a prevention strategy for ongoing sexual relationships and would be inappropriate here.

Clinical Management Algorithm

For this specific patient scenario:

1. Confirm sustained viral suppression: Verify HIV RNA <200 copies/mL on at least 2 consecutive measurements over the past 6 months 1
2. Assess and optimize ART adherence: Use validated adherence instruments and pharmacy refill data 1
3. Counsel on U=U: Explain that with continued adherence and viral suppression, sexual transmission risk is eliminated 1
4. Monitor regularly: HIV RNA testing every 3-6 months to ensure continued suppression 1
5. Screen for STIs: Recommend condoms for prevention of other sexually transmitted infections, not HIV transmission 1

Common Pitfalls to Avoid

• Do not recommend PrEP for partners of virally suppressed individuals—this represents unnecessary medication exposure and cost 1
• Do not undermine patient confidence in U=U—the evidence is robust that sustained viral suppression eliminates transmission 1
• Do not neglect adherence support—transmission risk returns if viral suppression is lost 1, 2
• Do not forget that U=U only applies after 3-6 months of documented suppression—earlier periods carry residual risk 1, 2