The HPV Vaccine

The HPV Vaccine
Having understood the pathogenesis of the virus, it is important to understand the mechanism of the HPV vaccine. In a research conducted by Walboomers et al, it was stated that the absence of HPV- negative cancers implied that effective prophylactic vaccination might eliminate cervical cancer worldwide.
Based on information available on FDA's website, the HPV vaccine is a recombinant vaccine. The genes that code for a specific protein, L1 protein, from each of the four virus types of the virus (6,11,16,18) are expressed in yeast to produce large quantities of that protein, which is purified to get the vaccine. The L1 protein rearranges itself to resemble the virus and hence are called Virus Like Proteins (VLP) (www.fda.gov).
HPV infects the cervical epithelium and expresses E6 and E7 proteins, which are potential oncogenes. The vaccine based on VLP, is injected with an adjuvant which generates antibodies that prevent infection. The VLPs in the vaccine present the immune system with the conformational, neutralizing epitopes found on the natural virus. It also regulates the immune system to generate antibodies that neutralize the effect of the virus and prevent infection if there is a future exposure. In case of an exposure, the vaccinated person's antibodies for the L1 protein coat the virus and prevent it from releasing any genetic material.(Dias et al 2005).
Gardasil, the first HPV vaccine approved by the FDA was available in 2006. Manufactured by Merck, the vaccine helps protects against all the four types of HPV virus; types 6 and 11 that cause genital warts and types 16 and 18 that cause cervical cancer. The vaccine is administered intra-muscularly in three doses over a span of six months(FDA approves..). According to the National Cancer Institute, the vaccine has been successful in preventing infection of the dominant HPV types, but it does not protect against the other strains of HPV that are also responsible for causing cervical cancer.
Cervarix, another HPV vaccine manufactured by GlaxoSmithKline, was approved by the European Union in 2007 and is being tested for approval in the U.S. Cervarix targets virus types 16 and 18 that cause cervical cancer. In the article,Vaccines and Immunizations published on the CDC website, recommends the vaccine for most women between the ages of 9-26 years with the exception of pregnant women since there isn't enough information available about the safety of the vaccine on a pregnant woman and her unborn child.
The safety of the vaccine, Gardasil, is closely monitored via Vaccine Adverse Event Reporting System (VAERS), Vaccine Safety Datalink project (VSD) and the Clinical Immunization Safety Assessment Network (CISA). Although, the vaccine has been quite safe overall, there have been 9,749 reports of adverse reactions. Of these, about 94% were non-serious and only 6% had serious adverse reactions. a few adverse reactions reported. According to CDC, the percentage of serious reports for Gardasil is less than the overall average of other vaccines. The most common side effect of the vaccine is soreness at the site of the injection.

Reference
Dias, Dennis, et al. “Optimization and Validation of a Multiplexed Luminex Assay To Quantify Antibodies to Neutralizing Epitopes on Human Papillomaviruses 6, 11, 16, and 18.”
Clinical and Vaccine Immunology, Vol 12, No.8, p. 959-969, August 2005 : American Society for Microbiology. Web. 1 December 2009.
“FDA approves Gardasil for use in boys and young men”. www.merck.com, n.d
Web. 30 November 2009.
<http://www.merck.com/newsroom/news-release- archive/product/2009_1016.html>
“Understanding cancer series: HPV Vaccine” www.cancer.gov. National Cancer Institute.
6 June 2006. Web. 1 December 2009.
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“Vaccines: Products.” www.merck.com, Gardasil, n.d
Web. 30 November 2009. >
“Vaccines, Blood and Biologics”, www.fda.gov. n.d
Web. 1 December 2009.

Walboomers, Jan, et al. “Human Papillomavirus Is a Necessary Cause of Invasive Cervical Cancer Worldwide.” Journal of Pathology, Vol 189 issue 1, pages 12-19 (1999): John Wiley and sons. Web. 1 December 2009.
“Vaccines and Immunizations” www.cdcgov. 22 July 2008. Web. 1 December 2009.
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