Monday, August 17, 2009

HPV vaccine

Human papillomavirus (HPV) vaccine is a vaccine that prevents infection with certain species of human papillomavirus associated with the development of cervical cancer, genital warts, and some less common cancers (e.g., anal, vulvar, vaginal,penile.

Two HPV vaccines are currently on the market: Gardasil and Cervarix. Both vaccines protect against two of the HPV types that can contribute to the development of cervical cancer, and some other genital cancers; Gardasil also protects against two of the HPV types that cause genital warts.

Public health officials in Australia, Canada, Europe and United States recommend vaccination of young women against HPV to prevent cervical cancer and genital warts, and to reduce the number of painful and costly treatments for cervical dysplasia, which is caused by HPV. Worldwide, HPV is the most common sexually transmitted infection in adults. For example, more than 80% of American women will have contracted at least one strain of HPV by age fifty.

Although most women infected with genital HPV will not have complications from the virus, worldwide there are an estimated 470,000 new cases of cervical cancer that result in 233,000 deaths per year. About eighty percent of deaths from cervical cancer occur in poor countries. In the United States, most of the approximately 11,000 cervical cancers found annually occur in women who have never had a Pap smear, or not had one in the previous five years.

Since the vaccine only covers some high-risk types of HPV, experts still recommend regular Pap smear screening even after vaccination.

Gardasil has been shown to also be effective in males, though it has not yet been approved by the FDA to be marketed as such.

Safety

Gardasil is a 3 dose (injection) vaccine. There have been 24 million doses distributed in the United States, and there have been 13,758 Vaccine Adverse Event Reporting System (VAERS) reports following the vaccination. Ninety-three percent were reports of events considered to be non-serious (e.g., fainting, pain and swelling at the injection site (arm), headache, nausea and fever), and 7% were considered to be serious (death, permanent disability, life-threatening illness and hospitalization). There is no proven causal link between the vaccine and serious adverse effects - all reports are related by time only. That is, they are only related because the effect happened some time after the vaccination.

There have been 39 deaths among women who took the vaccine reported to the CDC. Six are currently under investigation, and seven are unconfirmed because of a lack of patient identification information. None of the other 26 confirmed deaths were linked to the vaccine. Guillain-Barré Syndrome (GBS), a rare disorder that causes muscle weakness, has been reported after vaccination with Gardasil. There is no evidence suggesting that Gardasil causes or raises the risk of GBS. Additionally, there have been rare reports of blood clots forming in the heart, lungs and legs. Most of those who suffered blood clots were already at risk from other factors, such as taking oral contraceptives.

Based on all of the information they have today, CDC continues to recommend Gardasil vaccination for the prevention of 4 types of HPV. Merck, the manufacturer of Gardasil, will continue to test women who have received the vaccine to determine the vaccine's efficacy over a lifetime

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