Table 3.

Multisite HPV16/18 vaccine efficacy among individuals with evidence of a previous* HPV16 or HPV18 infection prior to vaccination†

Study population	Arm	Women or sites	No. events	HPV16/18 prevalence, %	Efficacy (95% CI), %
Cervical, anal, or oral HPV16/18	HPV vaccine	681	27	4.0	57.8 (34.4 to 73.4)
Multisite woman level‡	Control	703	66	9.4
Cervical HPV16/18	HPV vaccine	681	10	1.5	76.5 (54.6 to 88.8)
	Control	703	44	6.3
Anal HPV16/18	HPV vaccine	681	19	2.8	54.4 (22.4 to 73.9)
	Control	703	43	6.1
Cervical, anal, oral HPV16/18	HPV vaccine	2043	29	1.4	66.4 (47.0 to 78.6)
Multisite infection level§	Control	2109	89	4.2
HPV16/18 at two or three sites	HPV vaccine	681	2||	0.3	90.6 (65.8 to 98.5)
	Control	703	22||	3.1

* Defined as women who were human papillomavirus (HPV) 16 and/or HPV18 seropositive at baseline and cervical HPV16/18 DNA negative at baseline. CI = confidence interval; HPV = human papillomavirus.

† The vaccine efficacy for oral HPV16/18 alone was excluded given low number of events. These results are presented in Supplemental Table 2 (available online).

‡ A woman-level event is defined as a woman who is positive for cervical, anal, and/or oral HPV DNA at the four-year visit.§An infection-level event is defined as a woman’s anatomical site having HPV16/18 DNA (women contribute three times for each anatomic site); the vaccine efficacies for this analysis utilized generalized estimating equations to adjust for the correlation within an individual.|| Statistically significantly lower HPV16/18 concordance at two or more anatomic sites in HPV16/18-infected women in the HPV vaccine arm (7.4% [2/27] of HPV16/18-infected women) than the control arm (33.3% [22/66] of HPV16/18-infected women), P = .01.