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PrEP can further reduce the risk of HIV infection after a partner starts treatment
Liz Highleyman, 2016-07-21 05:50:00
Offering Truvada pre-exposure prophylaxis (PrEP) to the HIV-negative partner
in a serodiscordant couple during the first six months after the HIV-positive
partner starts antiretroviral therapy (ART) can serve as a 'bridge' to provide
further protection against HIV infection, researchers reported yesterday at
the 21st International AIDS Conference
(AIDS 2016) in Durban, South
Studies have shown that
effective antiretroviral treatment dramatically reduces the risk of onward HIV
transmission - a concept known as 'treatment-as-prevention' - and PrEP reduced
the risk of infection by more than 90% if taken consistently. Putting these two highly effective
approaches together may fill any gaps that can occur, for example, if a person
has recently started ART and not yet achieved an undetectable viral load.
Jared Baeten of the University of Washington in
Seattle presented findings from the Partners PrEP Demonstration Project, which
looked at the real-world feasibility of ART plus PrEP for serodiscordant (mixed
HIV status) couples in Africa.
The original Partners PrEP
study, which Dr Baeten first presented at the International AIDS
Society conference in 2011, randomly assigned
HIV-negative partners in serodiscordant
heterosexual couples in Kenya and Uganda to receive tenofovir/emtricitabine
(the drugs in Truvada), tenofovir
alone or a placebo. (At the time World Health Organization and country
guidelines recommended ART initiation based on CD4 cell count, not for everyone
diagnosed with HIV.)
The follow-up Partners PrEP Demonstration Project aimed to show whether an integrated combination
of PrEP for negative partners plus ART for positive partners could further
reduce the risk of HIV transmission. By the time this study started in November
2012 there was ample evidence that both PrEP and treatment-as-prevention were
effective, so all participants received both interventions on an open-label
The demonstration project was conducted at four centres in Kenya and Uganda that had
hosted the original Partners
PrEP randomised trial, but it enrolled a new cohort
of 1013 serodiscordant heterosexual couples in which neither partner had ever taken
The median age of participants was 30 years. In two-thirds
of couples the woman was the HIV-positive partner. Positive partners had a
median CD4 cell count of 436 cells/mm3 and a median viral load over
37,000 copies/ml. A majority (65%) said they'd had unprotected sex in the past
Upon enrolment the HIV-positive partner was offered
combination ART in accordance with national guidelines - under 350 cells/mm3
until mid-2013, then universal treatment thereafter - while the HIV-negative
partner was offered daily Truvada.
PrEP was continued as long as the positive partner delayed starting treatment,
or for the first six months after ART initiation, allowing time for viral load
to become undetectable; PrEP was extended if the positive partner had treatment
interruptions or known poor adherence.
The demonstration project selected couples
based on a risk algorithm that gave scores from 1 to 10, depending on predictors
of HIV risk including younger age, cohabitations rather than marriage, recent
unprotected sex, male partners not being circumcised and positive partners
having a high viral load; couples with a score of 5 or higher were eligible for
At the 2015 Conference on Retroviruses and Opportunistic
infections, Dr Baeten reported interim results showing that two
initially HIV-negative partners seroconverted. In lieu of a placebo arm, the
researchers used the incidence rate in the placebo arm of the original randomised
Partners PrEP trial to estimate that 40 new infections would have been expected
in the absence of ART and PrEP - a risk reduction of 96%.
week Dr Baeten gave final updated results with data through June 2016,
reflecting approximately 1,700 person-years of follow-up.
this time 91% of positive partners had started ART and almost all had achieved
viral suppression (<400 copies/ml). Most (97%) of the negative partners offered PrEP accepted it. Couples used ART
alone for 39%% of follow-up time, PrEP alone for 20%, overlapping ART and PrEP
for 33% and neither ART nor PrEP for 7%.
By the end of follow-up four new HIV infections had occurred,
compared with 83 expected without ART or PrEP, for a relative risk reduction of
95%. Protection was similar regardless of sex, age or pre-treatment viral load.
Adherence to both PrEP and ART was
good during the demonstration project. Among HIV-negative partners who started
PrEP and were randomly selected for drug level testing, 82% of blood samples showed
However, none of the newly infected
individuals were actually using ART and PrEP consistently - and in fact they were
in couples who used neither.
One woman had broken up with her positive
partner and stopped PrEP, while a second woman had a partner who did not yet want
to start treatment and she also stopped PrEP; neither woman had detectable
tenofovir in her blood at the time of infection. A third woman was a sex worker
who used PrEP inconsistently. The sole man who was infected declined PrEP and
had multiple sex partners.
"In this open-label
demonstration project of integrated delivery of ART and PrEP for prevention in
HIV serodiscordant couples, we observed virtual elimination of incident
HIV," the researchers concluded.
like this could have a substantial effect on the HIV epidemic," Dr Baeten
said at an AIDS 2016 press conference. "Both PrEP and ART are extremely
important interventions that can virtually eliminate HIV transmission."