HIV prevention

Background

• HIV elimination is possibly with the present tools, even without a cure or vaccine
• Strategies
  • Non-pharmacologic
  • Pharmacologic

Non-pharmacologic approaches

• Condoms
• Safe sexual practices
• Circumcision

Pharmacologic approaches

Treatment as Prevention (TasP)

• Basics
  • Screen everyone
  • Treat everyone at time of diagnosis
  • Treated individuals are less likely to transmit
    • U=U: undetectable equals untransmittable
  • Lowers the community viral load
• Cohen et al. NEJM 2016
  • 1763 serodiscordant couples in 9 countries who received early care (at time of diagnosis) or delayed care (wait until CD4 drops)
  • Outcome was transmission to their HIV-negative partners
  • 93% lower risk (HR 0.07) from your linked partner, with no linked infections when partner was virologically suppressed

Post-Exposure Prophylaxis (PEP)

• Basics
  • Potential HIV exposure
  • Short-term ARVs
  • Prevents HIV
• Reactive approach
• Guidelines exist, including Canada's PEP guideline 2017
• Exposures
  • Sexual
    • Consensual
      • Heterosexual
      • Homosexual
    • Non-consensual
      • Heterosexual
      • Homosexual
  • Non-sexual
    • Needlestick
    • Other
• Approach
  • Did an exposure occur?
    • Infected body fluid or mucosa that comes into contact with mucosa, blood, or broken skin
      • Infectious: blood, genital secretions, amniotic fluid, breast milk, CSF, pleural pericard, peritoneal synovial
      • Non-infectious: urine, saliva, sweat, emesis, feces
    • Details often hazy, with drugs, alcohol, and trauma
    • Often end up treating the worst-case scenarios
  • What is the risk per exposure to known HIV contact?
    • Very high risk
      • Blood transfusion 92.5%
    • High risk
      • Receptive anal intercourse 1.38%
      • Needle sharing 0.63%
      • Percutaneous needle-stick injury 0.23%
    • Moderate risk
      • Anal (insertive) 0.11%
      • Vaginal (receptive) 0.08%
      • Vaginal (insertive) 0.04%
    • Low risk (no specific numbers)
      • Oral sex (giving)
      • Oral sex (receiving)
      • Oral-anal contact
      • Sharing sex toys
      • Blood on compromised skin
• Treatment
  • Start within 72h, use 3 drugs, treat for 28 days
    • Truvada + raltegravir; but any will work
    • Avoid drugs in pregnant or breastfeeding women
  • Screen for
    • STIs
    • HBV and HCV, maybe HAV (for immunization)
    • Pregnancy
    • Trauma
  • Follow-up in 4-6 weeks then 4 months for repeat testing
  • Counsel patients on STIs, substance use, etc

Pre-Exposure Prophylaxis (PrEP)

• Basics
  • Give ARV to HIV-negative individuals who are at risk
  • If they are exposed, they won't seroconvert
• Proactive approach
• Only works if you take the pills (70-90% effective), but adherence is poor
• Guidelines exist, including Canada's PrEP guideline 2017
• Eligibility
  • MSM: multiple unprotected exposures, HIV+ partner, sex work
  • IVDU who share needles
  • Women: high number of unprotected partners, HIV+ partner, sex work
• Baseline
  • HBsAb, HBsAg, and HBcAb; HCV-Ab; and HAV, so you can vaccinate
  • STI screening
    • Syphilis, chlamydia, and gonorrhea
    • Urethral, pharyngeal, and rectal
• Treatment
  • Truvada 1 tablet daily for 3 months at a time, without repeats
  • Counsel on condom use and side effects
    • Needs to be taken for 7 days before it is effective
    • Connect to mental health and other services, if indicated
  • Follow-up every 3-4 months
    • Ask about HIV and STI symptoms, and screen them
    • Side effects of medications
    • Reassess need for PrEP
    • Screen for drug and alcohol abuse

Other modes of prevention

• On-demand PrEP, with each encounter
  • 2 tabs 2-24h before sex, then 1 tab at 24h after and 48h after
  • Limited utility, more cumbersome
• PEP-in-pocket (PIP)
  • Very infrequent condomless sex, 0 to 4 exposures per year
  • Rx for 28 days of Truvada that they can start when needed after an exposure
  • On exposure, start their own treatment and arrange followup in clinic