Hpv Vaccine and Cervical Cancer: is it Worth Vaccinating?

Over the past two years, the O-N-E L-E-S-S campaign for Gardasil, the new HPV vaccine to protect against cervical cancer, has brought discussion about the human papilloma virus to the forefront, shining new light not only on the vaccine itself, but also on the issues that surround it.

HPV is ubiquitous. Nearly 50% of sexually active people will have HPV at some point in their lives. There are around 20 million people with HPV infections in the U.S., with 6.2 million new cases occurring every year. The most serious consequence of HPV infections is cervical cancer, yet public knowledge about HPV is poor -- less than 50% of women have heard about HPV and its link to cervical cancer.

It's crucial that the public gains more knowledge about HPV and cervical cancer, particularly in the present climate where the merits of the vaccine have been clouded by a political rhetoric. Information on the link between HPV and cervical cancer, how common the disease is and who gets it, detection methods, other effects of the disease, and the role and effectiveness of the vaccine have to be addressed. Examining these topics will help guide decisions as medical professionals recommend this vaccination to a whole generation of 11-12 year old girls, and perhaps boys in the future.

The relationship between HPV and cervical cancer: There are over 100 types of HPV. About 15 of them are "high-risk" types that cause cervical cancer. HPV infections are more common in the younger population, with nearly 75% occurring in the 15-25 age group. Most HPV infections are "silent" -- people who carry the virus don't  know they have it and transmit it freely to their sexual partners. The good news, however, is that most of these infections are self-limiting, meaning that nearly 90% of them resolve on their own within 24 months without causing any problems. In a minority of people, however, the infections persist, either as a result of high-risk sexual behavior (such as multiple partners and unprotected sex), or weakened immunity because of smoking, stress, and long term use of certain medications like steroids. These factors can propel HPV infections to cause precancerous and cancerous lesions of the cervix. Over 99% of cervical cancers are caused by HPV. HPV infections are necessary, but not sufficient on their own to cause cervical cancer.

Pap tests and cervical cancer: A Pap test detects early changes in the cells of the cervix due to HPV or other effects, which if left untreated, may progress to cervical cancer. Fortunately, due to a well organized Pap test program in the U.S., the incidence of cervical cancer has dropped by 75% over the past 50 years. Therefore, for women who get regular Pap smears, the incidence of cervical cancer is low. Currently in the U.S., about 11,000 new cases of cervical cancer develop each year, and around 4,000 deaths occur from it. Even though one would wish that there were no cases of cervical cancers to reckon with, when compared to the number of HPV infections that occur each year, the ratio between HPV infections to cervical cancer is low. According to the American Cancer Society, four out of five women who died of cervical cancer did not have a Pap test in the previous five years. These numbers show that the Pap smear has been very successful in curtailing the incidence of cervical cancer in this country.


Role of the HPV vaccines in preventing cervical cancer: There are now two HPV vaccines available worldwide to protect against two major types of cancer-causing HPV. Gardasil, manufactured by Merck, has been available in the U.S. since June 2006. Cervarix, manufactured by Glaxo Smith Kline, is planned to be introduced in the U.S in late 2008 or early 2009. Both vaccines target HPV types 16 and 18, which cause the majority of cervical cancers. HPV type 16 causes nearly 50% of cervical cancers and HPV type 18 causes about 20% of cervical cancers. Clinical trials have shown that both vaccines prevent 70% of cervical cancers with almost 100% effectiveness. However, this only true when the person has been vaccinated prior to exposure to the virus types 16 and 18. The efficacy of the vaccine drops once these virus types gain access to the body. This is why the CDC recommends administering the vaccine to young girls, ages 11-12, before their sexual debut to obtain maximum benefit.

Pap test versus HPV Vaccine: Both Pap tests and the HPV vaccine prevent cervical cancer, but they do so in different ways. The vaccines produce antibodies to fight against the HPV virus well before it can invade the cervix. Therefore the vaccine prevents the development of any HPV related pathology on the cervix. On the other hand, the Pap test, detects abnormal changes in the cervix as a result of HPV, many of which require follow up visits and procedures in order to prevent these abnormalities from progressing to cancer. Most people would agree that prevention is better than detection or treatment. Managing abnormal Pap smears alone costs $2-3 billion a year in this country. But as the vaccine only provides protection against 70% of cervical cancers, Pap tests should be continued to detect the remaining 30% of cervical cancers that are not covered by the vaccine. It is important to note that apart from cervical cancer prevention, the vaccine has also been found to be beneficial against many other HPV related diseases, and it could eventually help in reducing the medical and emotional toll that such diseases take on people.

Those most prone to cervical cancer in the United States are those groups of people who have no access to Pap smears or will not obtain them because of inadequate access either as a result of poor socio economic status, poor knowledge or cultural differences. These groups are overwhelmingly comprised of women from ethnic minorities and whites in the Appalachian regions. Therefore, education aimed at the public should not only include comprehensive cervical cancer prevention programs in layman's terms, but also should be culturally sensitive to meet the needs of people from various backgrounds. The HPV vaccine has the potential to save millions of young lives and families, but, unless it reaches the same group of women who are not obtaining their Pap smears today, it will miss out on keeping its "one less" promise both here at home and around the world.


©2008 Shobha S. Krishnan, M.D.

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