Cervical cancer results in about 290,000 deaths worldwide each year. It is the major cause of cancer-related death in many countries and second most common female cancer in the world.

In the United States, it is estimated that about 10,400 new cases of cervical cancer are diagnosed each year and these result in approximately 3,700 deaths. This cancer and several other uro-genital cancers are caused by human papilloma virus (HPV). HPV types 16 and 18 have been linked most strongly to human cervical and other cancers and probably account for 70% of cases.

A recently developed quadrivalent recombinant vaccine containing HPV proteins made in yeast induces a strong immune response against human papilloma types 6, 11, 16 and 18. In a trial involving 25,000 women followed over two years, the vaccine (Gardasil, Merke and Co) was compared to a placebo. The women received three doses of the vaccine preparation. The women in the first group evaluated (12,000 individuals) were not infected with HPV at the time of vaccination and remained free of HPV16/18 during the study. The vaccine prevented 100% of high-grade cervical pre-cancers (cervical intraepithelial neoplasia (CIN 2/3)) and non-invasive cervical cancers (adenocarcinoma in situ (AIS)) associated with type 16 and 18 HPV. CIN2 is a moderate lesion of the cervix while CIN3 is a high-grade lesion. AIS is an early stage of cervical cancer. While no cases of CIN or AIS were found in the vaccine group, 21 cases were found in the placebo group.

In broader group of women, those in the first study plus those who became infected during the vaccination period or who may not have undergone the complete protocol, the vaccine reduced the risk of developing pre-cancer (CIN) or non-invasive cancer (AIS) by 97%. There was one case in the non-placebo group in the broader study.

There has been (May 2007) a three year follow up in this study. It was found that prevention of CIN2/3, AIS or cervical cancer was 98% in the vaccine-treated group.

The reason that the vaccine includes HPV type 6 and 11 epitopes is that, although these HPV types do not cause cancer, they can give false positive pap smears and also cause ano-genital warts. In the United States, about one million women per year are told they have "an abnormal Pap smear". This results in more tests, anxiety, and fear of possible cancer. Moreover, since ano-genital warts affect both sexes, the inclusion of type 6 and 11 epitopes might induce men to take the vaccine as well, thus stopping the spread from vaccinated men to unvaccinated women. The three year follow-up study demonstrated that the HPV vaccine showed 100% efficacy in ano-genital wart prevention.

This study has also shown that the quadivalent vaccine reduced the rate of vulvar or peri-anal lesions in patients who were HPV-infected at the start of the trial or who exhibited HPV-caused disease.