Results of CVT Study
CVT is an important source of data that has generated numerous scientific publications and continues to advance the science of HPV vaccination, natural history, and cervical cancer screening among vaccinated cohorts.
In addition to strong evidence for vaccine safety and efficacy, data from the trial demonstrated that three doses of the HPV vaccine may not be necessary, as similar vaccine efficacy against cervical HPV 16/18 infection was observed among women who received two, and even a single dose, after more than 10 years of follow-up.
Data from CVT has also demonstrated partial cross-protection against HPV 31, 33 and 45; high efficacy against HPV16/18-associated precancer for more than a decade after initial vaccination, supporting the notion that invasive cervical cancer is preventable; among women approaching screening ages, vaccinated as young adults and with a history of prior intensive screening, HPV-based screening modalities performed better than cytology; negative vaccine efficacy against high-grade cervical precancer caused by non-preventable HPV types, suggesting that unmasking could attenuate long-term reductions in high-grade disease following successful implementation of HPV vaccination programs in screened populations;
~10% HPV vaccine efficacy against carcinogenic HPV types excluding HPV 16, 18, 31, 33, 45; no vaccine efficacy against existing HPV infections; HPV type replacement does not occur among vaccinated individuals within 4 years and is unlikely to occur in vaccinated populations; antibodies generated by HPV infection provide some protection against re-infection; bivalent HPV vaccination does not have an effect in expediting clearance of nontargeted incident infections (pooled data from CVT and PATRICIA trial); strong protection against HPV infections at essentially all non-cervical anatomic sites where HPV causes cancer in women (i.e., anus, vulva, and oral region), and that the level of protection was comparably high to that observed at the cervix among the same women.
