Table 1. Summary of per-act anal intercourse HIV-1 transmission probability studies included in meta-analyses reported by Baggaley et al 2010⁵, Patel et al⁴, and the current analysis.

Reasons for study exclusion are provided, where applicable.

Study	Population, sample size, setting		Design. Study dates	Per-act estimate, % (95%CI)				Included in:
							Baggaley et al 2010	Patel et al 2014	Current analysis
URAI
DeGruttola et al 198919	132 MSM (some infected, some uninfected) plus 155 sexual partners, US		Retrospective-partner, study dates not stated	0.5-3.0a			✓	✓	✓
Leynaert et al 199820	72heterosexual couples (male index) practising AI, Europe		Retrospective-partner, 1987-1992	3.38		(1.85-4.91)	✓	✓	✓
Vittinghoff et al 199918	1583 MSM, US		Prospective cohort of individuals, 1992-1994	0.82		(0.24-2.76)	✓	✓	× Supersededc
Halperin et al 2002 (abstract)6 plus S.C. Shiboski (personal communication, 2003)	59 heterosexual couples (male index), US		Retrospective-partner, participants recruited 1985-1986	0.4		(0.08-2.0)b	✓	× Estimate interpreted as a relative risk	× Abstract pre-2013
Jin et al 20107	1427 MSM, Australia		Prospective cohort of individuals, 2001-2007	0.91d		(0.41-2.07)	× Data not yet published	✓	✓
Scott et al 20148	MSM, US Pre-ART N=1813 c Early ART N=10,760f		Four prospective cohorts of individuals: Jumpstart 1992-199515, EXPLORE 1999-200313, VAX 004 1998-200214, VPS 1995- 199916, 17	0.60e 0.73f		(0.34-1.09) (0.45-0.98)	× Data not yet published	× Not includedg	✓
Smith et al 20159	3490 MSM, US		Two prospective cohorts of individuals: EXPLORE 1999-200313, VAX 004 1998-200214	1.11h 0.41i		(0.75-1.62) (0.30-0.55)	× Data not yet published	× Data not yet published	× Study data reported by Scott et al 2014 8
UIAI
Vittinghoff et al 199918	1583 MSM, US		Prospective cohort of individuals, 1992-1994	0.06		(0.02-0.19)	× Estimate is per partner of HIV-1 positive or unknown serostatus	✓	× Estimate is per partner of HIV-1 positive or unknown serostatus; supersededc
Jin et al 20107	1427 MSM, Australia		Prospective cohort of individuals, 2001-2007	0.16		(0.05-0.31)	× Data not yet published	✓	✓
Scott et al 20148	MSM, US Pre-ART N=1813c Early ART N=10,760f		Four prospective cohorts of individuals: Jumpstart 1992-199515, EXPLORE 1999-200313, VAX 004 1998-200214, VPS 1995- 199916, 17	0.14e 0.22f		(0.04-0.29) (0.05-0.39)	× Data not yet published	× Not includedg	✓
Smith et al 20159	3490 MSM, US		Two prospective cohorts of individuals: EXPLORE 1999-200313, VAX 004 1998-200214	0.27h 0.20i		(0.18-0.41) (0.15-0.27)	× Data not yet published	× Data not yet published	× Study data reported by Scott et al 2014 8

NS – not stated.

^aRange rather than 95%CI reported by publication.

^bRange rather than 95%CI.

^cEstimate superseded by reanalysis of the dataset reported in Scott et al 2014⁸.

^dJin et al⁷ published per-act risk with ejaculation taking place inside the rectum (1.43%, 95%CI 0.48-2.85%) and with withdrawal prior to ejaculation (0.65%, 95%CI 0.15-1.53%). Per-act estimate regardless of when ejaculation occurred was reported in Patel et al⁴, obtained from study authors (James Jansson, personal communication).

^eData taken from the pre-ART era (estimates use data from the Jumpstart study¹⁵).

^fData taken from the early ART era (estimates use data from the EXPLORE¹³, VAX 004¹⁴, and VPS^{16, 17} studies).

^gData mentioned in text but not included in meta-analysis

^hData taken from the EXPLORE study¹³, restricted to study participants reporting never using condoms.

ⁱData taken from the VAX 004 study¹⁴, restricted to study participants reporting never using condoms.