SEPTEMBER 30, 2007
VOLUME 4 NO. 16

EDITORIAL

OPINION

Canada's not ready for universal HPV immunization


The federal government's $300 million handout to jumpstart provincially funded immunization programs for HPV vaccine Gardasil has met with support from many public health agencies, but scepticism from many in general practice, myself included. The vaccine will now be provided by the governments to school age kids in Grades 7 and 8 in more than half the country.

Cervical cancer is the eleventh most common cause of cancer in women, afflicting 1,350 Canadian women, and causes the deaths of 400 per year. The HPV vaccine is meant to make inroads where other public health measures have failed, immunizing girls who have not yet experienced intercourse and are therefore unexposed to HPV. Vulnerable groups include immigrant and Aboriginal women, and the disabled, each of whom may miss PAP screening for reasons of culture, language, education, poverty or distance from healthcare facilities.

That all sounds great, but there are several issues at play here:

Efficacy Studies seem to show Gardasil to be quite effective in limiting precancerous changes caused by HPV serotypes 16 and 18, responsible for 70% of cervical cancers, and types 6 and 11, responsible for 90% of genital warts. Unfortunately, while results were significant for Grade II dysplasia, as an NEJM editorial stated, they were "insufficient to support a conclusion of efficacy for grade 3 cervical intraepithelial neoplasia or adenocarcinoma in situ," which are considered better markers for cervical cancer.

Other strains The new GSK vaccine Cervarix, approved in Australia and the EU, protects against strains 31 and 45 (in addition to 16 and 18) and therefore would cover an additional 10% of cervical cancers but would not protect against genital warts. Given that 31 is the predominant strain among targeted high risk groups such as the Inuit in Nunavut, this might be the better vaccine for such groups.

Risky behaviour Some worry an HPV vaccine will inadvertently increase adolescents' sense of invulnerability, decreasing the frequency of PAP smears, thus ultimately increasing the cervical cancer risk. They fear a repeat of what happened among certain groups at high risk for HIV, who decreased condom use after the introduction of antiretrovirals.

Longterm effectiveness We currently have no idea of the length of immunity and whether booster shots will be required in the future and if so, with what frequency. The number of girls under 16 who were tested was also small, less than 3000.

Vaccine refusal There is also a possibility of increase in general vaccine refusal, which some family physicians have seen with the introduction of seven new needles in infancy (Prevnar, Menjugate and Varivax) in addition to DPTP, H flu and MMR vaccines. If herd immunity for any of the basic vaccines is compromised or if adolescents or young adults miss necessary boosters, the consequences for public health could be quite negative.

Safety Complaints involving Gardasil, filed with the FDA, cite a statistically significant increase in Guillain-Barre Syndrome.

Cost Is Gardasil the most cost effective measure for Public Health? A BC Cancer Agency study projects health care costs to be six times those saved with 26 year followup. Putting resources of the order of magnitude of investment in Gardasil into determining barriers to PAP smear screening and promoting education and novel ways of approaching the issue such as self administered PAP smears could prove more cost effective.

With so many unanswered questions and the potential for harm, we physicians must ask — why the rush? What is the crisis that precludes Canadians from waiting for more data, from examining the benefits of other vaccines, and from inviting the input from a dispassionate, independent and expert review body such as the Cochrane Collaboration, to make the best informed decision possible? Failure in this venture can only damage the image of public health in Canada. — Dr Neil Arya, Waterloo, ON

 

 

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