Table 3.

Estimated effectiveness of a comprehensive safer conception package to prevent HIV transmission based on a historical cohort

	Expectation from the Partners PrEP study		Observed from the SCIP study		Incidence rate ratio (95% CI)	p‐value
	N incident infections/N years of follow‐upa	Incidence (95% CI)b	N incident infections/N years of follow‐upa	Incidence (95% CI)b
All sites in the Partners PrEP Study
Overall incidencec	2.1/64.8	3.23 (0.0, 8.0)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	0.12
By genderd	3.0/64.6	4.67 (0.0, 10.9)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	0.04
By agee	1.9/65.5	2.90 (0.0, 7.8)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	0.15
Restricting to the Thika, Kenya site from the Partners PrEP Study
Overall incidencec	2.9/65.1	4.39 (0.0, 9.8)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	0.05
By genderd	2.9/65.4	4.36 (0.0, 9.6)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	0.04
By agee	2.6/65.0	3.99 (1.5, 8.0)	0.0/61.6	0.00 (0.0, 6.0)	0.00 (Undefined)	<0.001

^aThe number of expected seroconversions and person‐years do not sum precisely to the overall totals because each subgroup estimate is drawn from a separate bootstrapped counterfactual cohort model; ^bPer 100 person‐years. The incidence is calculated with a modified intention‐to‐treat analysis approach, where Partners PrEP participants who were found to have prevalent HIV infection at enrolment were excluded from the sample; ^cIn this analysis, the counterfactual population was sampled to match the distribution of pregnancy risk score in the SCIP sample; ^dIn this analysis, the counterfactual population was sampled to match the distribution of pregnancy risk score and gender of the HIV‐negative partner in the SCIP sample; ^eIn this analysis, the counterfactual population was sampled to match the distribution of pregnancy risk score and age of the HIV‐negative partner in the SCIP sample.