October 13, 2011
Vaccine and cancer experts in Australia have defended criticism of the Australia’s HPV vaccination program.
The criticisms have been raised by Judy Wilyman, who is completing a PhD on the Australian government’s vaccination policy at the University of Wollongong.
“There is inconclusive evidence it will reduce any cervical cancer and the long-term risks of using this vaccine have not been determined,” says Wilyman, who has a Master of Science in population health, and recently outlined her concern in an online article published by the British Society for Ecological Medicine.
Australia was one of the first countries in the world to adopt a public vaccination program in 2007, targeting two specific strains of the human papillomavirus (HPV 16 and HPV 18), which experts believe are the most important strains in cervical cancer.
The vaccine is routinely delivered to girls in the first year of secondary school, and about 70 per cent of girls are reported to have been vaccinated so far.
But, says Wilyman, the population-wide vaccination program is not justified because the potential benefits and risks of the vaccine are still unclear.
Firstly, she says, evidence suggests there are other factors that just as important in causing cervical cancer.
“HPV is a necessary factor but it’s not an ‘independent’ factor in development of cervical cancer,” says Wilyman. “HPV infection with any strain is not sufficient on its own to induce cervical cancer.”
She says 90 per cent of women infected with any strain of HPV do not develop cervical cancer.
“This evidence supports the conclusion that environmental and lifestyle factors are a determining cause in conjunction with HPV in the progression to cervical cancer,” says Wilyman.
She argues that the risk of cervical cancer is increased by low socio-economic status, low sanitation and hygiene, multiple sexual partners, and infections with other viruses such as herpes.
Wilyman says this is why, for example, developed countries have about four times lower cervical cancer rates than developing countries, despite having a similar, if not slightly higher, prevalence of HPV.
Role of HPV defended
Cancer and vaccine experts aren’t convinced by Wilyman’s arguments, saying the HPV vaccine is the best way to prevent cervical cancer.
“One of the best things you can do for your daughter is to have her vaccinated against HPV,” says Associate Professor Karen Canfell at Cancer Council NSW, adding that it is a leading form of cancer among women.
She says recent evidence from the International Agency for Research on Cancer shows that HPV rates do track cervical cancer rates if you take into consideration screening, which allows early intervention in cervical cancer.
Canfell agrees the majority of HPV infections don’t lead to cervical cancer and that some other factors are required for a woman to develop cancer.
“It’s termed a necessary but not sufficient cause,” says Canfell, an epidemiologist specialising in cervical cancer.
She says according to IARC studies the main “cofactors” that accelerate the progression of cervical cancer are a woman giving birth to a high number of children, giving birth at a younger age, using oral contraception and smoking.
But Canfell says despite these cofactors, HPV is the “primary cause” of cervical cancer, and this is exactly the rationale behind having an HPV vaccine.