Cancer vaccine shows promise

By Dr. Ananya Mandal, MDJun 17 2011

In the latest research news, a cervical cancer vaccine programme has produced the first evidence of disease prevention among treated women. This vaccine targets human papillomavirus (HPV), the virus believed to trigger cervical cancer in women.

Now the scientists in Australia have found that introducing the vaccine led to a reduced incidence of high-grade abnormal cells that are precursors to cancer. Among girls under the age of 18, incidences of high-grade cervical abnormalities (HGAs) fell by a statistically significant 0.38% – almost halving the numbers, from 0.80% to 0.42% they explained. But there was no drop in the numbers of women with cervical abnormalities who were older than 17. This is unsurprising since the vaccine is known to be most effective if given to girls before they become sexually active.

The HPV vaccination programme was introduced in Australia for all women aged 12 to 26 between 2007 and 2009. Researchers compared HGA rates before and after the start of the programme.

The team leader Dr Julia Brotherton, from Victorian Cytology Service Registries in Melbourne with her colleagues wrote, “This is the first report of a decrease in incidence of high-grade cervical abnormalities within three years after implementation of a population-wide HPV vaccination programme.” The report appeared in The Lancet medical journal.

Kate Broun, Cancer Council Victoria's cancer screening manager, added, “This is encouraging data and a good first indication that the Human Papilloma Virus (HPV) vaccine is effective at preventing cervical cell abnormalities. However this is only suggestive evidence and we really need to see the link with Pap (papillomavirus) test registers to confirm this.”

“The not-so-cautious optimist in us wants to hail this early finding as true evidence of vaccine effect,” write Dr Mona Saraiya and Dr Susan Hariri of the Centres for Disease Control and Prevention in Atlanta, US, in a linked commentary for the journal. But they said they wanted to know more about the vaccine status of the individuals (each woman is supposed to have three shots) and wanted more work to establish whether the reductions in potential cancers were really a result of vaccination or some other cause.

Michael Quinn, professor of gynecology and gynecologic oncology at the University of Melbourne, said, “The study is the first anywhere in the world to show falling rates of high-grade change in very young women. Although this is likely to be due to the effects of the vaccination programme, further analysis of information linking women's smear history to their vaccination history will be needed to prove that the fall is entirely due to vaccination rather than other factors.”

“The study looked at overall trends, and we cannot be absolutely certain that the drop in cervical abnormalities in the youngest age group was due to HPV vaccination,” said Associate Professor Karen Canfell, an epidemiologist with the Cancer Council of New South Wales. “The group in which the effects were observed were younger than the age group in whom screening is normally recommended, so although the results are suggestive, there are some issues in interpreting the findings,” she added.

The UK introduced its own cervical cancer vaccination programme in September 2008, offering the jab in school to 12- and 13-year-old girls, with catch-up programs for those up to 18. The cost was expected to be £100m a year. In spite of worries that parents would refuse to have their daughters vaccinated against what is essentially a sexually-transmitted virus, the take-up has been good, according to figures from the Department of Health. In the school year 2009/10, more than three-quarters of 12- to 13-year-olds were given all three doses of the vaccine.

Public health experts say that women should not assume they are not vulnerable to the disease after vaccination and should still go for regular screening checks. The study, which took place in Victoria state in Australia, was conducted independently without any corporate funding.