Experimental HPV Vaccine Cervarix Does Not Accelerate Clearance Of Virus
Experimental HPV Vaccine Cervarix
GlaxoSmithKline'sexperimental human papillomavirus vaccine Cervarix does not acceleratethe clearance of HPV among women infected with the virus and should notbe used to treat infection, according to a National Cancer Institute-funded study published Wednesday in the Journal of the American Medical Association, the Wall Street Journal reports (Rubenstein, Wall Street Journal, 8/15).
Cervarixhas been shown to be 100% effective in preventing infection with HPVstrains 16 and 18, which together cause about 70% of cervical cancercases. Researchers in a 2006 study published in the online edition ofthe Lancet also found that Cervarix prevented infectionwith HPV strains 31 and 45, which together with strains 16 and 18,cause more than 80% of cervical cancer cases.
The Australian Therapeutic Goods Administrationin June approved the vaccine for girls and women ages 10 to 45, and theEuropean Committee for Human Medicinal Products last month recommendedthe vaccine for sale and marketing in the European Union. FDA has granted a standard 10-month review of the vaccine and most likely will take action on GSK's application in January 2008, according to analysts at Evolution Securities (Kaiser Daily Women's Health Policy Report, 7/20).
For the study, Allan Hildesheim, a senior investigator at NCI, andcolleagues between June 2004 and December 2005 enrolled 2,189 womenages 18 to 25 in Costa Rica who tested positive for HPV DNA at the timeof enrollment. About half of the women in the study were given Cervarixand half were given the hepatitis A vaccine.
According to thefindings, 33.4% of the women who received Cervarix had cleared HPVinfection after six months, compared with 31.6% in the control group(Hildesheim et al., JAMA, 8/15). After one year, 48.8% ofwomen who received Cervarix had cleared the infection, compared withabout 49.8% who had not received the vaccine (Picard, Globe and Mail,8/15). The study also found that most HPV infections, regardless of thestrain, clear spontaneously over a period of six months to two years (Wall Street Journal, 8/15).
"You should not get [Cervarix] because you want to treat an existing infection," Hildesheim said (Steenhuysen, Reuters,8/14). He added, "The question that has not yet been answered iswhether protecting [a woman] from reinfection of a virus that she haspreviously been infected with, and successfully cleared, will in factreduce that woman's risk of getting cervical precancer and cancer" (Wall Street Journal, 8/15).
GSK spokesperson Liad Diamond, said the results of the study are "completely expected." GSK and Merck,which makes the HPV vaccine Gardasil, said their vaccines are notintended to treat existing infections, adding that the study's findingsconfirm their companies' research (Reuters, 8/14).
Lauri Markowitz, a medical epidemiologist and director of the HPV working group at CDC, in an accompanying JAMA editorial wrote that the study shows that Cervarix "has no therapeutic efficacy," the Globe and Mail reports (Globe and Mail,8/15). However, she noted that a woman who has one type of the HPVvirus "could benefit from protection against" another type, adding thata woman who had and cleared an HPV vaccine-type infection "mightbenefit from boosting the antibody response and increased protectionfrom future reinfection" with the same HPV strain.
Accordingto Markowitz, research to "further address" these questions might beavailable from ongoing vaccine trials (Markowitz, JAMA,8/15). In addition, Markowitz wrote that the study's findings, coupledwith the high risk of contracting HPV after the onset of sexualactivity, demonstrates the importance of administering the vaccine inthe early teenage years (Globe and Mail, 8/15).
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