Researchers have reported that women who are positive for HPV DNA, do not benefit from Cervarix, a vaccine against HPV 16/18 L1 virus-like particle.
HPV is the sole cause of cervical cancer, and types 16 and 18 are the most common. The seven most prevalent types of HPV cause almost 90% of all cases of cervical cancer while types 16 and 18 are the cause of approximately 70% of all cases.
Cervical cancer can occur from 2 to 50 years after the onset of infection.
Cervarix is 90.4% effective in preventing cervical intraepithelial neoplasia ( CIN ) 2+ related to HPV 16/18 in previously unexposed women.
Gardasil, a quadravalent vaccine against HPV types 6/11/16/18 has been approved by the FDA ( Food and Drug Administration ) for vaccination of young girls and women.
Most studies of Cervarix and Gardasil have shown that vaccination has little impact on infected women. This is the reason vaccination is recommended for young girls before sexual exposure.
In the present study, there was no evidence of increased viral clearance at 6 or 12 months in women between the ages of 18 and 26 who had HPV DNA.
The researchers observed clearance of HPV-16/18 in 33.4% of the vaccine group and 31.6% of the control group at six months. Clearance was observed at 12 months in 49% of the vaccine group and 50% of the control group.
An accompanying editorial has emphasized the fact than HPV vaccines have diminished effectiveness with age as most infections are acquired at an early age.
Source: Journal of AmericanMedical Association, 2007