Vaccination against human papillomavirus

[Three of the authors respond:]

We wrote our commentary1 hoping to initiate a broader discussion about how limited public resources are allocated, about the kinds of questions and concerns that might be addressed before programs are initiated and about the place of HPV vaccinations in an overall cervical cancer prevention policy that is already having success in Canada through the use of Pap smear testing. We maintain this focus here.

We thank James Mansi for responding for Merck Frosst but note that he does not actually address our concerns directly. We acknowledge the points he has raised; however, even adding the 3 components Mansi includes in the “new standard of care” (proper education, continued Pap smear testing and post-vaccination surveillance) will still leave a vaccination program insufficient. We also need — at the least — much improved cervical cancer screening programs and vaccine registries, as well as better knowledge of the prevalence of HPV strains and of the duration of protection before we consider mass vaccination programs. Moreover, we must determine whether and how vaccinating girls and women (who are already mostly well protected by their own immune systems, safer sex practices and existing screening programs) would actually change the inequitable death rates from cervical cancer in Canada.

That Eduardo Franco and colleagues would consider our cautionary position “irrelevant and untenable” is most puzzling. We are pleased to see that James Brophy, by contrast, finds it “sagacious.” The precautionary principle is one that many people apply in assessing public health programs (see www.sehn.org/precaution.html for a discussion of this principle). Furthermore, we clearly stated that HPV was a necessary — but not sufficient — cause of cervical cancer; what, then, is the purpose of Franco and colleagues' example of smoking and lung cancer?

More importantly perhaps, we never questioned the selection of young women aged 15–25 years for participation in studies of the vaccine's efficacy, nor did we question the facts that immune responses in adolescents may be stronger than those in young adults and that vaccination is of maximal benefit when used for pre-exposure prophylaxis. We did ask, however, if 5 years of trials provided enough information to proceed with a mass vaccination program given that the vaccine's effectiveness rates are just starting to be known. (In response to Alex Ferenczy, we point out that our comment about the trials available for review was based on data presented by Lisa Rambout and colleagues:2 only 3 of the 6 studies meeting their inclusion criteria for systematic review were of the quadrivalent vaccine. This would seem to be a “handful.”)

Nevertheless, and notwithstanding the “utmost scientific rigour” of the randomized controlled trials (although Brophy has raised some interesting issues about this), about half of the 50 000 girls and women in the vaccine trials participated in studies of the bivalent HPV vaccine, Cervaris, which we did not discuss in our commentary. As well, the published report of the study by Reisinger and colleagues describes the experiences with Gardasil of only a limited number of girls aged 9–15 years (617 in the vaccinated group, 322 in the control group), which is the main age range for immunization in Canada, and provides data only on immunogenicity and short-term safety, not on efficacy.3 Thus, conflating all of the girls and women who were studied with this very small group of particular interest is inappropriate.

Alan Cassels repeats, while most others ignore, the basic question our commentary raised for discussion: Why begin mass vaccinations now? Where is the evidence base for this important public health decision? The letter writers who confuse the issue of epidemics with details of the ways in which women with cervical cancer suffer deflect this question. They also perhaps ignore the current gaps in care that may explain why many women ultimately diagnosed with invasive cervical cancer did not have a Pap smear test when it was due despite having received care from physicians in the previous 5 years (Ms. Kathleen Decker, CancerCare Manitoba: personal communication, 2007).

Women, and men, suffer in myriad ways, and public health policies need to focus on where best to allocate finite resources, not only on an individual level but also with regard to population needs. This means that cost-effectiveness and lost opportunity costs are usually taken into account. As Schiffman has pointed out in the US context, “It is worth debating … whether immediate, universal coverage is a greater public health priority … than other needs … competing for the same resources.”4 We need to have this debate in Canada. In addition, with regard to Jeff Nisker's distinction between individual decisions about the use of the vaccine and public policies about a program of vaccinations, we need to emphasize that both personal and population health care must always be based on the primary principle of “do no harm.”

Wynia recently wrote that “this vaccine still faces plenty of questions.”5 We hope readers will continue to discuss these questions and the place of HPV vaccination in a broad sexual and reproductive health perspective and to accept alternative viewpoints generously and in reasoned fashion, even ones that question supposedly “established” wisdom.