Population effectiveness, not efficacy, should decide who gets vaccinated against human papillomavirus via publicly funded programs.

Persistent infections by carcinogenic or high-risk genotypes of human papillomavirus (HPV) have been proved to be the cause of virtually all cervical cancer and are also associated with cancers of the vagina, vulva, penis, oropharynx, and anus [1–3]. Low-risk genotypes of HPV have been shown to be the cause of genital warts (Condyloma acuminata), a common sexually transmitted disease that has a heavy disease burden for both genders because the easily recurring disease is difficult to cure [4]. Consequently, the socioeconomic costs of HPV-induced diseases are enormous. The discovery of the role of HPV in human cancers and other morbidities has led to revolutionary advances in cervical cancer prevention, including the development of prophylactic HPV vaccines. Two HPV vaccines are currently available and US Food and Drug Administration approved: (1) Gardasil (Merck), which targets HPV16 and HPV18, the 2 most carcinogenic HPV genotypes that account for 70% of cervical cancer, and HPV6 and HPV11, which cause 90% of genital warts; and (2) Cervarix (GlaxoSmithKline), which targets HPV16 and HPV18. To date, HPV vaccination against HPV16 and HPV18 among HPV-naive women has proved to be nearly 100% efficacious in preventing the incidence of related cervical precancerous lesions for approximately 5–6 years after vaccination [5]. However, HPV vaccination does not increase the clearance of preexisting HPV infections and related lesions [6, 7]. Therefore, HPV vaccination of the general population is less effective than in selected, HPV-naive women because some sexually active women are already infected by the targeted HPV genotypes at the time of vaccination and therefore do not experience a benefit in preventing disease attributed to that HPV infection [8]. It is also important to note that with increasing age there are fewer incident infections and, thus, fewer infections prevented by HPV vaccination in absolute terms, although efficacy for incident infections among HPV-naive women remains excellent [8]. In addition there is now some compelling evidence that young, HPV-naive men are also highly protected against incident HPV infection [9]. This finding has triggered an intensive debate about the added value of providing boys with a routine HPV vaccination program, supplementing the existing female-only programs [10–15]. Those who advocate offering the quadrivalent HPV vaccination to boys emphasize that vaccination can directly benefit men with high risk of contracting HPV-related viral infections and cancers, particularly men who have sex with men (MSM); that vaccinating boys would increase the vaccination impact on women by providing herd immunity; and that vaccinating boys would demonstrate that both men and women are equally socially responsible for sexual health [10–12]. However, there are also cogent arguments against vaccinating boys [13–15]. First, the protective efficacy of male vaccination has not been fully demonstrated, so the additional cost-effectiveness of adding boys in the vaccination program may be overestimated for men. Second, men can benefit from herd immunity of Received 20 April 2011; accepted 21 April 2011. Potential conflicts of interest: P. E. C. is compensated for serving on a data safety and monitoring board for human papillomavirus vaccines for Merck but does not participate in the clinical trials of Gardasil. F. -H. Z. participates in and receives compensation for clinical trials to evaluate both Gardasil (Merck) and Cervarix (GSK) in China. Correspondence: Philip E. Castle, PhD, MPH, American Society for Clinical Pathology Institute, 1225 New York Ave, NW, Suite 250, Washington, DC, 20005 (philip.castle@ ascp.org). The Journal of Infectious Diseases 2011;204:335–37 The Author 2011. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals. permissions@oup.com 0022-1899 (print)/1537-6613 (online)/2011/2043-0003$14.00 DOI: 10.1093/infdis/jir287