What is the best recommendation to reduce the risk of infectious disease transmission in a patient who injects fentanyl daily, shares equipment with a partner, and has a negative HIV (Human Immunodeficiency Virus) status, normal renal function, and positive antibodies for hepatitis A and B, but negative for hepatitis C?

HIV Pre-Exposure Prophylaxis for People Who Inject Drugs

Offer daily emtricitabine/tenofovir disoproxil fumarate (TDF/FTC) for HIV pre-exposure prophylaxis (Answer A). This patient has substantial HIV risk through sharing injection equipment (cookers, cottons, water) with her injecting partner, and TDF/FTC is the evidence-based intervention that directly reduces her risk of HIV acquisition.

Risk Assessment and Rationale

This patient demonstrates high-risk behavior for HIV transmission despite using sterile syringes:

• Sharing injection equipment (cookers, cottons, water) carries significant HIV transmission risk, even when syringes themselves are not shared 1
• Multiple daily injections with a primary partner who shares equipment creates ongoing exposure risk 1
• The CDC recommends PrEP for populations with HIV incidence above 2% per year, which includes people who inject drugs sharing equipment 2

Evidence for PrEP in People Who Inject Drugs

Daily TDF/FTC has demonstrated >90% efficacy in preventing HIV acquisition in injection drug users when adherence is maintained 3, 4:

• Placebo-controlled trials specifically included injection drug users who share equipment and showed significant risk reduction 3, 4
• Efficacy exceeds 90% with adequate adherence, though effectiveness is highly correlated with adherence levels 3
• Only 2% of individuals discontinue PrEP due to adverse effects 3, 5

Why TDF/FTC Over TAF/FTC

TDF/FTC (Answer A) is preferred over TAF/FTC (Answer B) for this patient:

• TDF/FTC has extensive safety and efficacy data in people who inject drugs from randomized controlled trials 3, 4
• TAF/FTC lacks comparable evidence in this population and is not the standard recommendation 2
• Her normal renal function (eGFR >60 mL/min) eliminates concerns about TDF-related nephrotoxicity that would favor TAF 2

Why Not Hepatitis Vaccination

Hepatitis B vaccination (Answer C) is inappropriate because she already has protective immunity:

• Positive hepatitis B surface antibody with negative surface antigen indicates prior vaccination or resolved infection with immunity 1
• Re-vaccination provides no additional benefit 1

Hepatitis A vaccination (Answer D) is also inappropriate because she has existing immunity:

• Positive hepatitis A antibody indicates prior infection or vaccination with lifelong immunity 1
• Re-vaccination is unnecessary and does not address her primary HIV risk 1

Implementation Strategy

Pre-initiation requirements 2:

• HIV antigen/antibody testing (already completed and negative)
• Creatinine clearance assessment (already completed, eGFR >60)
• Hepatitis B and C screening (already completed)
• Comprehensive STI screening should be performed
• Pregnancy test (for reproductive-aged women)

Monitoring schedule 2:

• HIV testing every 2-3 months (quarterly follow-up)
• STI screening every 3-6 months
• Creatinine clearance at 3 months, then every 6 months
• Pregnancy testing at each visit

Critical Counseling Points

PrEP does not replace harm reduction strategies 1:

• Continue using sterile syringes from the exchange program for each injection
• Stop sharing cookers, cottons, and water—these are the primary HIV transmission risks in her current practice 1
• Use sterile or boiled water to prepare drugs 1
• Use a new or disinfected container (cooker) and new filter (cotton) for each injection 1

Adherence is paramount 3, 6:

• Daily dosing is essential—efficacy drops dramatically with missed doses 3, 6
• In women, effectiveness requires consistent adherence due to lower tissue drug concentrations 2, 6
• Minimum 7-day lead-in period is needed to achieve adequate tissue protection 2

PrEP does not prevent other infections 2:

• No protection against hepatitis C (she remains HCV antibody negative and at risk) 1
• No protection against bacterial infections causing abscesses
• Regular STI screening remains essential 2

Substance Use Treatment Referral

While PrEP addresses HIV risk, substance abuse treatment should be offered concurrently 1:

• Cessation of injection drug use is the only way to eliminate injection-related HIV transmission risk 1
• Methadone maintenance or other medication-assisted treatment reduces risky injection behaviors 1
• This referral complements but does not replace PrEP initiation 1

Common Pitfalls to Avoid

• Do not delay PrEP while waiting for substance abuse treatment engagement—HIV prevention should begin immediately 1
• Do not assume sterile syringe use alone provides adequate protection—sharing any injection equipment transmits HIV 1
• Do not prescribe TAF/FTC based solely on theoretical renal advantages—TDF/FTC is the evidence-based standard for this population 2, 3
• Do not revaccinate against hepatitis A or B when antibodies are already present—this wastes resources and does not address HIV risk 1