Authors' objectives:

This report aims to assess the efficacy of HPV vaccine.

Authors' results and conclusions: Bivalent vaccine (types 16 and 18) The efficacy of the vaccine was evaluated in a double blind, placebo controlled RCT in 1113 women, from 15 to 25 years of age, performed in the U.S., Canada and Brazil. The follow-up was 4.5 years. Seroconversion occurred in 95% of the women. Protection against persistent infection (more than a year) took place in 100% of the women who received vaccine. The efficacy regarding the incidence of infection (new infection) was 96.9%. More than 99% of the patients vaccinated sustained the level of protective antibodies for more than 4.5 years, against both viral types studied. No case of cervical intraepithelial neoplasia (CIN) was observed in the vaccine group, versus 8 cases reported for the placebo group. In another study conducted in 776 women 15-55 years old with a 4.5 year follow-up, the bivalent vaccine showed similar results including women in the elder group (46 to 55 years old). Tetravalent vaccine (types 6; 11; 16 and 18): The efficacy of the tetravalent vaccine was assessed in a Phase IIB RCT conducted in 552 women (average age 20 years old) carried out in the U.S., Europe and Brazil. The follow-up was over 48 months. The results were statistically significant with p <0.001 for the following observations: Overall protection against persistent infection for types 16 and 18 occurred in 89% of the patients with 100%, 86% and 89% for types 6, 16 and 18, respectively. There were no cases of HPV11. Protection against CIN occurred in 100% of the intervention group. Seven cases of CIN were seen in the placebo group. Protection against all external genital warts caused by HPV 6-11 took place in 100 % of the participants; 7 were seen in the placebo group. Vaccine efficacy against the 4 types was 90% (95% CI 71-97%). In a Phase III double blind RCT including more than 12,000 women 16-26 years old, with a two-year follow-up, 9 cases of CIN or adenocarcinoma in situ were detected in the vaccine group, whereas 143 in the placebo (94% efficacy). Nine cases of external genital warts were observed in the vaccine group, versus 174 in the placebo (95% efficacy). The vaccine was well tolerated and there were no serious adverse effects. At present, there are several international Phase III RCTs being performed for both vaccines; on the whole they include more than 40,000 patients and they will continue in the next coming years.

Authors' recommendations: The RCTs identified showed a high degree of efficacy in young women in preventing premalignant lesions associated to the types of HPV included. This would imply a long term reduction in the incidence of cancer due to HPV. In addition, the tetravalent vaccine lowered the incidence of vulvar and vaginal lesions, as well as genital warts. The length of protection is still to be known; the protecting antibodies persist for at least 4 years. It is estimated that vaccine boosts should be given at 7-10 year intervals. It is worth mentioning that the beneficial effects regarding incidence and prevalence of cervical cancer in the general population can take decades to become clear. Even though the vaccine seems to be a major breakthrough in cervical cancer prevention, at present, it does not replace the need to use preventive strategies such as PAP smear screening, since prophylaxis is not against all types of HPV. It is yet to be determined what the best vaccination strategy would be at a sanitary level, and the cost-effectiveness at local level when compared with the different prevention strategies.

Authors' methods: Overview

Project Status: Completed

URL for project: http://www.iecs.org.ar/

Year Published: 2006

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Argentina

Organisation Name: Institute for Clinical Effectiveness and Health Policy

Contact Address: Dr. Emilio Ravignani 2024, Buenos Aires - Argentina, C1414 CABA

Contact Name: info@iecs.org.ar

Contact Email: info@iecs.org.ar

Copyright: Institute for Clinical Effectiveness and Health Policy (IECS)