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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