Experimental HPV Vaccine Cervarix Does Not Accelerate Clearance Of Virus, Study Says

Main Category: Cervical Cancer / HPV Vaccine
Article Date: 17 Aug 2007 - 3:00 PDT

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GlaxoSmithKline's experimental human papillomavirus vaccine Cervarix does not accelerate the clearance of HPV among women infected with the virus and should not be 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).

Cervarix has been shown to be 100% effective in preventing infection with HPV strains 16 and 18, which together cause about 70% of cervical cancer cases. Researchers in a 2006 study published in the online edition of the Lancet also found that Cervarix prevented infection with HPV strains 31 and 45, which together with strains 16 and 18, cause more than 80% of cervical cancer cases.

The Australian Therapeutic Goods Administration in June approved the vaccine for girls and women ages 10 to 45, and the European Committee for Human Medicinal Products last month recommended the 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).

Study, Reaction
For the study, Allan Hildesheim, a senior investigator at NCI, and colleagues between June 2004 and December 2005 enrolled 2,189 women ages 18 to 25 in Costa Rica who tested positive for HPV DNA at the time of enrollment. About half of the women in the study were given Cervarix and half were given the hepatitis A vaccine.

According to the findings, 33.4% of the women who received Cervarix had cleared HPV infection after six months, compared with 31.6% in the control group (Hildesheim et al., JAMA, 8/15). After one year, 48.8% of women who received Cervarix had cleared the infection, compared with about 49.8% who had not received the vaccine (Picard, Globe and Mail, 8/15). The study also found that most HPV infections, regardless of the strain, 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 is whether protecting [a woman] from reinfection of a virus that she has previously been infected with, and successfully cleared, will in fact reduce 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 not intended to treat existing infections, adding that the study's findings confirm their companies' research (Reuters, 8/14).

JAMA Editorial
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 HPV virus "could benefit from protection against" another type, adding that a woman who had and cleared an HPV vaccine-type infection "might benefit from boosting the antibody response and increased protection from future reinfection" with the same HPV strain.

According to Markowitz, research to "further address" these questions might be available from ongoing vaccine trials (Markowitz, JAMA, 8/15). In addition, Markowitz wrote that the study's findings, coupled with the high risk of contracting HPV after the onset of sexual activity, demonstrates the importance of administering the vaccine in the early teenage years (Globe and Mail, 8/15).

The study abstract is available online.

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