Two cases of HIV transmission on tenofovir DF monotherapy

Simon Collins, HIV i-Base

Case studies were recently published of two men who became HIV positive even though they were using daily tenofovir DF to treat hepatitis B (HBV).

The cases are important because this provides evidence that in the context of good adherence that both tenofovir DF and FTC might be needed to reach close to 100% protection for men.

Both cases were in gay men with good adherence. This was demonstrated by undetectable HBV viral load without blips for >3 years supported by pharmacy records, and by therapeutic drug levels tenofovir at the time of HIV diagnosis.

One case was diagnosed in acute HIV infection following 4 day of flu-like symptoms after an exposure risk – and 10 days after a negative antibody test. Viral load was <50 copies/mL.

The second case was identified after hospitalisation for severe seroconversion illness, diagnosed with a viral load of 160,000 c/mL.

Both men had immediate escalation to full ART – within approximately three weeks after likely date of infection – but this did not prevent infection. Established infection was verified by HIV total DNA and integrated DNA in both cases.

The results are also important because the WHO currently recommend tenofovir DF as a single drug option for PrEP based on non-significant differences compared to tenofovir DF/FTC in the (heterosexual) PARTNERS PrEP study.


While these two cases show proof of principle that infection is possible in the presence of likely good adherence to tenofovir, the absence of a denominator makes it impossible to quantify the level of risk.

The cases show the likely importance of dual therapy for PrEP which for many people is important for achieving close-to 100% protection. The results also support people at risk of HIV infection who are being treated for HBV switch to tenofovir/FTC for their HBV treatment.

These cases were first presented at conferences in Glasgow in 2014 and at BHIVA in 2015. [2, 3]


  1. Fox J et al. Tenofovir disoproxil fumarate fails to prevent HIV acquisition or the establishment of a viral reservoir: two case reports. Infect Dis Ther. Published online: 09 January 2016. DOI 10.1007/s40121-015-0102-x.
  2. Davies O et al. Failure of daily tenofovir to prevent HIV transmission or the establishment of a significant viral reservoir despite contin-ued antiretroviral therapy. 14th International Congress on Drug Therapy in HIV Infection, 23-26 October 2014, Glasgow. Poster abstract P199.
  3. Fox J et al. Pre-exposure prophylaxis fails to prevent HIV-1 infection or the establishment of a significant viral reservoir. 21st BHIVA conference, 21-24 April 2015, Brighton. Poster abstract P10. (PDF)

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