The HPV Vaccine

Abstract

In 1999, the Morbidity and Mortality Weekly Report (MMWR) identified the ten most significant public health achievements of the last 100 years (Table 1). (1) First on the list of accomplishments was vaccination, a biomedical and public health success story responsible for saving millions of lives and preventing untold misery from infectious diseases. Both life expectancy and quality of life have improved because of vaccines that have eradicated diseases such as smallpox, and virtually eliminated childhood diseases such as measles, diphtheria and pertussis (whooping cough). A particularly good example of the impact of vaccines are ones developed to combat infantile paralysis (polio), first by Salk, and later, by Sabin. Between 1951 and 1954, immediately prior to the widespread dissemination of Salk's polio vaccine, there were over 16,000 cases of paralytic poliomyelitis, and an average of 1900 U.S. deaths annually from polio. (2) The Salk vaccine was licensed in the U.S. in 1955, and cases of the disease dropped precipitously to fewer than 1000 per year until 1962, when the Sabin vaccine was licensed and administered on a widespread basis. (2) By the end of 1962, fewer than 100 cases were seen annually. There has not been a naturally occurring case of polio in the United States since 1979. (3) Concerted efforts by health and non-profit organizations to disseminate the polio vaccine have reduced the global burden of polio from approximately 350,000 cases per year in the late 1980s to 1200 cases in 2005, the 50th anniversary of the development of the vaccine. (4) A new vaccine has been developed and released for use against a leading cause of death in women worldwide--cervical cancer. The human papillomavirus, or HPV, a species-specific DNA virus with over 100 types identified to date, has been recognized as the causal agent in the development of cervical cancer. It also is associated with other cancers (e.g., anal, penile, vulvar, vaginal, and oral-pharyngeal). Over 30 types of HPV are anogenital, and approximately half of those are oncogenic. If left untreated, they have the ability to progress to invasive cancers. Other anogenital HPV types, known as low-risk types, are responsible for genital warts. Whereas genital warts are benign, they are visible and may be a source of embarrassment. HPV is common--a recent U.S. study concluded that overall prevalence among 14-24 year-old women, an age group included in the age range targeted for the HPV vaccine, is 33.8%, and that: This prevalence corresponds with 7.5 million females with HPV infection, which is higher than the previous estimate of 4.6 million prevalent HPV infections among females in this same age group in the United States. (5(p817)) Furthermore, the lifetime likelihood of acquiring HPV is estimated to be 75% or more. (6) Fortunately, infection with HPV also is transient, and in most cases, will clear up through the body's own immune response. According to the National Cancer Institute, about 10% of women have an oncogenic HPV infection at a given time, and they are more common in young women than in older women. Most cervical infections, including ones involving oncogenic types of HPV, clear on their own without causing cancer. (7) In the U.S., cervical cancer incidence and deaths have significantly decreased because of a well-designed and effective screening program, with an estimated number of 11,150 invasive cervical cancer cases, and 3670 deaths forecast for 2007. (8) Globally, the picture is grim as more than 250,000 women die annually from cervical cancer, making it the second most common cause of cancer death in women. Moreover, the World Health Organization anticipates a 25% increase in cervical cancer deaths over the next decade if significant interventions do not occur. (9) In addition, 80% of the approximately half million women who will be diagnosed with cervical cancer worldwide live in resource-poor developing countries that do not have the infrastructure to provide cytology screening for the disease. …