American Journal of Law & Medicine

Potential barriers to HPV immunization: from public health to personal choice.

INTRODUCTION

Of the over 100 types of human papillomavirus (HPV), more than 40 can be sexually transmitted. (1) Genital HPV infection is very common, with a point prevalence among women worldwide of approximately 10 percent. (2) In most cases, HPV infection is either cleared or becomes undetectable and causes no disease; however, persistent HPV infection is causally related to all cervical cancers and genital warts. (3) In addition, a large proportion of other cancers, such as vaginal, vulvar, anal, and penile cancers as well as many cancers of the head and neck, are associated with HPV infection. (4) Moreover, recurrent respiratory papillomatosis (RRP) is a potentially serious disease caused by HPV types typically responsible for genital warts. (5) RRP can lead to severe airways obstructions and may require repeated surgical interventions. HPV types are typically divided into high-risk types, most often associated with cancers, and low-risk types, typically associated with warts. High-risk types 16 and 18 are responsible for approximately 70 percent of cervical cancers worldwide, (6) whereas low-risk types 6 and 11 are responsible for approximately 90 percent of genital warts. (7)

Within the U.S. and worldwide there are tremendous disparities with respect to the incidence of HPV-related morbidity and mortality. In the U.S., cervical and other HPV cancers occur disproportionately among poor and minority populations. (8) Internationally, the burden of HPV-associated cancers disproportionately falls on developing countries, particularly those in sub-Saharan Africa and in Central and South America. (9) Most of these disparities are related to the lack of adequate screening programs available and the associated low rates of early detection and treatment.

In June 2006 the U.S. Food and Drug Administration (FDA) licensed an HPV vaccine produced by the pharmaceutical company Merck & Co., Inc. This vaccine, a quadrivalent vaccine, protects against persistent infection with four anogenital types of HPV (6, 11, 16, and 18) most frequently associated with genital disease as well as precancerous cervical lesions (or cervical precaneers) and external anogenital lesions (including anogenital warts) caused by the types. (10) The Centers for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practice (ACIP) recommended the vaccine for females ages 9 to 26, with a particular focus on 11- and 12-year-old girls. (11) A second vaccine, developed by GlaxoSmithKline (GSK), is under review for licensure by the FDA. This bivalent vaccine protects against persistent infection with HPV 16 and 18 and precancerous cervical lesions due to these types, but does not include protection against the types responsible for most genital warts. (12) Worldwide, the quadrivalent and bivalent vaccines have been approved for use in many industrialized and developing nations, though relatively few developing countries have been able to implement HPV immunization programs.

Research studies on both vaccines indicate very high levels of efficacy against persistent infection and anogenital disease due to HPV types targeted by these vaccines. (13) Aside from minor reactions, such as tenderness at the site of injection, few side effects have been attributed to HPV vaccination. (14) Follow-up studies indicate that both vaccines confer protection against precancerous cervical lesions for at least five years, (15) with some indirect evidence suggesting that protective immunity may last much longer. (16) The research indicates that the vaccines act in only a preventive manner and therefore do not provide protection in females who are infected with vaccine-related types at the time of vaccination. (17) Because HPV is a common infection, by early adulthood many women and men have already been infected by one or more HPV types. As a result, the efficacy of vaccination decreases with age (that is, with sexual activity). (18) In addition, studies indicate that vaccination of pre- and early-adolescents results in a stronger immune response than the response achieved with vaccination of young women in their late teens and early twenties. (19)

Both HPV vaccines have the potential to significantly reduce the enormous financial and human costs associated with cervical and other cancers. However, HPV vaccination can only fully deliver on its promise if vaccine is widely available and broadly accepted. In this paper, I plan to discuss some of the issues and challenges associated with developing successful HPV immunization strategies. First, this article will critically examine two commonly used approaches to vaccination (clinic-based versus school-based). Next, it will discuss barriers associated with delivering HPV vaccine to developing countries. Finally, in light of new evidence of HPV vaccine efficacy with males, it will address issues related to inclusion of males in HPV immunization programs.

I. POLICIES REGARDING IMPLEMENTATION OF HPV IMMUNIZATION

Different countries have differing policies with respect to child and adolescent immunization. These various approaches to immunization have implications for vaccine coverage and potentially for increasing or decreasing health disparities. In the U.S. vaccines typically are delivered in medical settings, requiring visits to doctors' offices or clinics. Immunization visits are integrated into, and used to encourage participation in regularly scheduled well-child health care. (20) A difficulty associated with the delivery of a preadolescent/adolescent multi-dose vaccine, like HPV vaccine, is that regularly scheduled well-health care visits for adolescents, unlike earlier childhood visits, are not a standardized part of the U. …

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