Imperial College London


Faculty of MedicineSchool of Public Health

Professor of Mathematical Epidemiology



+44 (0)20 7594 3263mc.boily




LG26Norfolk PlaceSt Mary's Campus






BibTex format

author = {Baggaley, R and Owen, B and Silhol, R and Elmes, J and Anton, P and McGowan, I and van, der Straten A and Shacklett, B and Dang, Q and Swann, EM and Bolton, DL and Boily, MC},
doi = {10.1111/aji.13039},
journal = {American Journal of Reproductive Immunology},
title = {Does per-act HIV-1 transmission risk through anal sex vary by gender? An updated systematic review and meta-analysis},
url = {},
volume = {80},
year = {2018}

RIS format (EndNote, RefMan)

AB - Quantifying HIV1 transmission risk peract of anal intercourse (AI) is important for HIV1 prevention. We updated previous reviews by searching Medline and Embase to 02/2018. We derived pooled estimates of receptive AI (URAI) and insertive AI (UIAI) risk unprotected by condoms using randomeffects models. Subgroup analyses were conducted by gender, study design, and whether antiretroviral treatment (ART) had been introduced by the time of the study. Two new relevant studies were identified, one of which met inclusion criteria, adding three new cohorts and increasing number of individuals/partnerships included from 1869 to 14 277. Four studies, all from highincome countries, were included. Pooled HIV1 risk was higher for URAI (1.25%, 95% CI 0.55%2.23%, N = 5, I2 = 87%) than UIAI (0.17%, 95 % CI 0.09%0.26%, N = 3, I2 = 0%). The sole heterosexual URAI estimate (3.38%, 95% CI 1.85%4.91%), from a study of 72 women published in a peerreviewed journal, was significantly higher than the menwhohavesexwithmen (MSM) pooled estimate (0.75%, 95% CI 0.56%0.98%, N = 4, P < 0.0001) and higher than the only other heterosexual estimate identified (0.4%, 95% CI 0.08%2.0%, based on 59 women, excluded for being a pre2013 abstract). Pooled peract URAI risk varied by study design (retrospectivepartner studies: 2.56%, 95% CI 1.20%4.42%, N = 2 (one MSM, one heterosexual); prospective studies: 0.71%, 95% CI 0.51%0.93%, N = 3 MSM, P < 0.0001). URAI risk was lower for studies conducted in the ART era (0.75%, 95% CI 0.52%1.03%) than preART (1.67%, 95% CI 0.44%3.67%) but not significantly so (P = 0.537). Prevention messages must emphasize that HIV1 infectiousness through AI remains high, even in the ART era. Further studies, particularly among heterosexual populations and in resourcelimited settings, are required to elucidate whether AI risk differs by gender, region and following populationlevel ART scaleup.
AU - Baggaley,R
AU - Owen,B
AU - Silhol,R
AU - Elmes,J
AU - Anton,P
AU - McGowan,I
AU - van,der Straten A
AU - Shacklett,B
AU - Dang,Q
AU - Swann,EM
AU - Bolton,DL
AU - Boily,MC
DO - 10.1111/aji.13039
PY - 2018///
SN - 1046-7408
TI - Does per-act HIV-1 transmission risk through anal sex vary by gender? An updated systematic review and meta-analysis
T2 - American Journal of Reproductive Immunology
UR -
UR -
VL - 80
ER -