A new international trial on the human papillomavirus (HPV) vaccine Gardasil confirms it is 98 per cent effective at preventing pre cancerous cervical growths in young women not already infected with HPV-16 or HPV-18, the two strains thought to be responsible for causing most cervical cancers.
The new study is published in today’s issue of the New England Journal of Medicine (NEJM), which also contains other articles on HPV and vaccination, including one on HPV and throat cancer, and a discussion on the debate surrounding the controversial introduction of HPV vaccination for young women in the US.
Gardasil, which is made by Merck, is designed to prevent four types of HPV: types 16 and 18, which causes 70 per cent of cervical cancers, and types 6 and 11, which cause genital warts. All four types are sexually transmitted forms of HPV.
The phase III study was supported by Merck and is called Future II. It followed over 12,000 women and girls aged from 15 to 26 years in 13 countries for 3 years. The participants were randomly assigned to receive either Gardasil or a placebo. As well being randomized, the trial was double blind, so neither the participants nor their doctors knew if they were receiving the drug or the placebo.
The vaccine was administered as three injections given on day 1 and then in months 2 and 6 of the trial.
The primary analysis of the trial was to examine the effectiveness of the vaccine in young women who were not already infected with HPV, since this is the purpose of vaccination, to prevent infection and not to treat already infected patients.
Around 10,500 participants, split half and half between placebo and vaccine groups, fell into this category; none of them showed signs of having the HPV-16 or HPV-18 virus up to one month following the third dose (month 7).
The main outcomes the scientists looked for were pre cancerous lesions (cervical intraepithelial neoplasia grade 2 or 3), a stage 0 cancer (adenocarcinoma in situ) or cervical cancer related to HPV-16 or HPV-18.
The results showed that in the uninfected subset (the majority of the participants) the vaccine was 98 per cent effective at preventing the pre cancerous growths. Overall, taking into account the women who were already infected, this figure went down to 44 per cent.
The authors concluded that:
“In young women who had not been previously infected with HPV-16 or HPV-18, those in the vaccine group had a significantly lower occurrence of high-grade cervical intraepithelial neoplasia related to HPV-16 or HPV-18 than did those in the placebo group.”
This is the strongest evidence so far that Gardasil is likely to be highly effective at preventing the majority of cervical cancers.
Dr Kevin Ault of Emory University School of Medicine in Atlanta, Georgia, US, and study co-author said:
“The goal of the study was to see if we could prevent pre-cancerous cases and we were 98 per cent effective.”
The US Centers for Disease Control and Prevention (CDC) has said the HPV vaccine should be given to all schoolgirls aged 11 and 12 as part of routine school vaccination programmes. Many health professionals support this view, as do women’s groups, some of which have lobbied federal and state government bodies to bring in legislation to make HPV vaccination for young women compulsory.
Some parent groups are fighting against this because they say vaccinating women at such a young age is interefering with their sexual development and may even be counterproductive and promote promiscuity. They also say it is interfering with their parental right to decide when their daughters should be vaccinated against a sexually transmitted disease.
Another study in today’s issue of the NEJM describes a new reason to be concerned about HPV. This time it includes men as well as women. Scientists are saying that HPV (transmitted through oral sex) is a common cause of throat cancer, which affects 11,000 Americans a year.
However, the greatest public health concern is still cervical cancer. The CDC estimates that more than 20 million Americans have HPV strains that are linked to cervical cancer.
Cervical cancer is the second biggest cause of cancer deaths among women worldwide and kills 240,000 women every year.
“Quadrivalent Vaccine against Human Papillomavirus to Prevent High-Grade Cervical Lesions.”
The FUTURE II Study Group.
N Engl J Med 2007 356: 1915-1927.
Volume 356:1915-1927, May 10, 2007, Number 19.
Written by: Catharine Paddock
Writer: Medical News Today