HIV incidence is high among gay men who use post-exposure
prophylaxis (PEP), investigators from Amsterdam report in the online edition
Overall, users of PEP were almost four times more likely to
become infected with HIV than gay men who did not use the therapy.
There was no evidence that PEP failure was the cause. The
investigators believe this is because PEP users continued to put themselves
risk of HIV after completing their treatment.
“Our study showed a high incidence of HIV among MSM [men who
have sex with men] who used PEP, an indication of ongoing risk behaviour,”
write the investigators. “This implies that PEP alone for this group is not
sufficient to prevent HIV infection, and a combination of other more
comprehensive preventative strategies is needed.”
HIV post-exposure prophylaxis is a four-week course of
combination antiretroviral therapy, prescribed after an encounter with body
fluids possibly infected with HIV.
It is estimated that the treatment can reduce the risk of
infection by up to 81%.
Gay men are the group most likely to request PEP after a
possible sexual exposure to HIV.
Australian research has shown that gay men who used PEP continued to be
at risk of HIV after completing their treatment.
Therefore, Dutch investigators compared HIV incidence among
gay men prescribed PEP in Amsterdam between 2000 and 2009, and compared this to
the rate of new infections seen over the same period among gay men enrolled in
the Amsterdam Cohort Study.
A total of 355 men who received 395 PEP prescriptions were
included in study. The majority of individuals took one course of PEP, but
approximately 10% of men were provided with multiple prescriptions (two to
Adherence rates were high, with 94% of men completing their
therapy. HIV status was monitored three and six months after baseline.
Eleven PEP users seroconverted. Two men tested HIV-positive
at their three-month follow-up appointment; one individual who did not attend
for his three month appointment was diagnosed at month six; and the remaining
eight men were HIV-negative at month three, but were HIV-positive at month six.
This provided an HIV incidence of 6.4 per 100 person years
among the individuals treatment with PEP.
The comparison population consisted of 782 men monitored in
the Amsterdam Cohort Study over the same period. In all, 67 of these men
seroconverted, providing an incidence rate of 1.6 per 100 person years.
The investigators calculated that men who were prescribed
PEP were almost four-times more likely to seroconvert than gay men in the
cohort study who did not use this therapy (IRR = 3.9; 95% CI, 2.1-7.4).
“We cannot completely rule out PEP failure in our study,”
comment he authors. However, they think this is unlikely.
They explain, “the majority of seroconverters tested
HIV-negative 3 months after PEP prescriptions, indicating that HIV acquisition
was most likely not related to the initial sexual contact for which PEP was
Moreover, “the majority of HIV seroconverters in the current
study reported to staff…that they had ongoing risk behaviour after PEP
PEP alone may be insufficient to prevent high-risk gay men
from infection with HIV, conclude the authors. They advocate a “combination
prevention” approach for these individuals, including counselling and pre-exposure
prophylaxis (PrEP). “MSM PEP users may well be suitable participants for such
PrEP intervention trials.”