Study details
During the period 2004-2005, the investigators randomly assigned 3,727 women aged 18-25 years to receive Cervarix and 3,739 to a control group that received the hepatitis A vaccine; after 4 years, the control group also received Cervarix and exited the study. They were replaced by an unvaccinated control group of 2,836 women. The new control group and the original HPV vaccine group were followed for an additional 7 years.
In years 7-11 of the trial, the investigators found 9.2 additional cervical intraepithelial neoplasias of grade 2 or worse (CIN2+) from HPV types not covered by Cervarix per 1,000 vaccinated women in comparison with unvaccinated participants. This corresponds to –71.2% negative vaccine efficacy against CIN2+ lesions of HPV types not covered by the vaccine.
There were 8.3 additional CIN3+ lesions from nontargeted HPV strains per 1,000 vaccinated women in comparison with unvaccinated participants, which corresponds to –135% negative vaccine efficacy.
Overall, however, there was a net benefit of vaccination, with 27 fewer CIN2+ lesions when all HPV genotypes – vaccine covered or not – were considered per 1,000 vaccinated women over the entire 11 years of follow-up.
There were also 8.7 fewer CIN3+ lesions across all genotypes per 1,000 vaccinated women, but the benefit was not statistically significant.
Among the study limits, the team was unable to evaluate the effect of clinical unmasking on cervical cancer, because women were treated for high-grade cervical lesions before cases could progress to cervical cancer.
The trial was funded by the National Cancer Institute and the National Institutes of Health Office of Research on Women’s Health. GlaxoSmithKline provided the Cervarix vaccine and supported aspects of the trial. Two authors are named inventors on U.S. government–owned HPV vaccine patents with expired licenses to GlaxoSmithKline and Merck. Dr. Steben is an adviser/speaker for many companies, including GlaxoSmithKline and Merck.
A version of this article first appeared on Medscape.com.