We appreciate the comments by Vidulich et al concerning the role of heterosexual anal intercourse (HAI) in anal human papillomavirus (HPV) acquisition. We agree that HAI is likely underreported, and that condoms are strongly recommended for prevention of sexually transmitted infection transmission for both women and men engaging in anal receptive intercourse.

There were 2 studies in our review that specifically addressed anal HPV in the context of HAI. Goodman et al, evaluating a cohort of healthy adult women in Hawaii, found that: (1) 29% of women reported ever having HAI; and (2) the risk of an incident anal HPV infection among women with a preceding concordant cervical HPV infection was 20.5 (95% confidence interval [CI], 16.3–25.7) whereas the risk of a cervical HPV infection after an anal HPV infection with a concordant genotype was 8.8 (95% CI, 6.4–12.2). Moreover, in the absence of a self-reported history of anal sex, they found that the risk of acquiring concordant anal HPV genotypes was higher after documented infection of those genotypes in the cervix (63% of infections) compared to acquiring the anal HPV genotypes prior to infection in the cervix (48% of infections), demonstrating that anal HPV infection occurs in the absence of HAI, and is highly correlated to cervical HPV infection. In the second study, Castro et al reported that rate of HAI was 21.4% among young Costa Rican women. Multivariate analysis found that concurrent cervical HPV, history of HAI with at least 2 partners, and lifetime number of sexual partners ≥4 had odds ratios (95% CI) of: 4.8 (3.9–5.9), 2.8 (1.7–4.5), and 2.3 (1.7–3.1), respectively. Thus, the rates of HAI reported in these studies by Goodman et al and Castro et al are similar to those reported by Benson et al by age and ethnicity, and based on the data from Goodman et al, we maintain that women can have anal HPV in the absence of HAI.

Because our publication was a systematic review of other previously published literature in the last 2 decades, the data provided in our article were summaries of previous studies. As a result, there were no studies in our review that reported the rates of squamous cell cancer of the anus among women who had received prophylactic HPV vaccination. However, we do hope that research conducted in the next several decades will be able to demonstrate the impact of prophylactic HPV vaccination on squamous cell cancer of the anus incidence.