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Friday, May 11th 2007

So, What Does This Say About The HPV Vaccine?

I think the Los Angeles Times is focusing on the wrong thing with their summary of a new study on the efficacy of the HPV vaccine in the NEJM,

Although the vaccine, called Gardasil, blocked about 100% of infections by the two human papilloma virus strains it targets, it reduced the incidence of cancer precursors by only 17% overall.

[W]hen Koutsky and her colleagues considered lesions caused by all strains of the virus, the vaccine reduced the risk by only 17%.

Because researchers had previously believed that 50% of all serious precancerous lesions were caused by types 16 and 18, this rate of protection seemed inexplicably low.

Dr. George F. Sawaya and Dr. Karen Smith-McCune of UC San Francisco called the benefits of the highly touted vaccine “modest,” and said that young women and their parents should take “a cautious approach” to vaccination because of the many unanswered questions about its efficacy.

“The effect is fairly small,” Sawaya said in a telephone interview. “The recommendation for widespread vaccination of women after they become sexually active may need to be rethought.”

Sawaya suggested in the editorial he co-wrote that the small size of the protection could be because other strains of HPV are filling the gap when types 16 and 18 are eliminated.

After finishing the article you might think the Los Angeles’ Times denouncement of the Merck’s HPV vaccine as inefficacious had some bearing on the real debate going on in this country – mandating the HPV vaccine for school age girls.

It doesn’t. Indeed, in many ways the FUTURE II study further defines the necessity of immunizing girls at school age.

Look the vaccine does what it is supposed to do. Yes, there are limitations to it:

  • It only protects against two of the four major oncogenic Human Papilloma Viruses
  • Not all cervical cancers are associated with HPV infection
  • You must be immunized prior to HPV 16 or 18 infection (basically before the start of sexual activity)

But this study opens up no NEW limitations. It protects against 16 and 18 very well, as the data shows.

When administered to subjects who had not been previously exposed to either HPV-16 or HPV-18, the prophylactic HPV vaccine was highly effective (98%) in preventing HPV-16–related and HPV-18–related cervical intraepithelial neoplasia grade 2 or 3 and adenocarcinoma in situ.

Drs. Sawaya and Smith-McCune’s most dramatic claim, in their accompanying editorial, is without basis. Namely the claim that,

In contrast to a plateau in the incidence of disease related to HPV types 16 and 18 among vaccinated women, the overall disease incidence regardless of HPV type continued to increase, raising the possibility that other oncogenic HPV types eventually filled the biologic niche left behind after the elimination of HPV types 16 and 18.

As the FUTURE Study investigators point out and cite on,

Speculation that elimination of HPV-16 and HPV-18 will open a niche for other high-risk viruses is not supported by the literature. Young women are often infected with multiple high-risk HPV types, and the risk of new infection is greater for women who are infected with one or more HPV types than for uninfected women.

What the LA Times fails to address is that the real public debate is over the mandates for vaccination. The American Cancer Society doesn’t even recommend HPV vaccine for all women, exactly because of what could easily have been predicted and what was found in this study – once you’re infected with 16 and 18 the efficacy is in the toilet. No duh.

Despite Sawaya and Smith McCune’s warnings,

[A] cautious approach may be warranted in light of important unanswered questions about overall vaccine effectiveness, duration of protection, and adverse effects that may emerge over time.

The vaccine has proven to do exactly what it has always claimed to – lower the rate of HPV 16 and 18 associated pre-neoplastic lesions (and thus the rate of HPV 16 and 18 associated cervical cancer) – when given to women before infection with serotypes 16 and 18,

Among women who tested negative for both HPV-16 and HPV-18 at enrollment (4693 in the vaccine group and 4703 in the placebo group), high-grade cervical disease developed in 95 subjects in the vaccine group and in 130 in the placebo group, a reduction of nearly 27% in the vaccine group.

For some, as the Los Angeles Times mentions, this is disappointing since

researchers had previously believed that 50% of all serious precancerous lesions were caused by types 16 and 18, this rate of protection seemed inexplicably low.

But the vaccine is still a success. All this might do is raise issues of the cost-benefit equation for the HPV vaccine.

For the real debate – over the mandating of the vaccine – the FUTURE II study does several things:

  • It further smites arguments over the safety of the vaccine
  • It deals a blow to mandate opponent arguments over the efficacy of the vaccine at preventing HPV 16 and 18 associated lesions in pre-infected girls
  • It provides some support for those who argue that the benefits are outweighed by the costs of the vaccine

The Los Angeles Times, as a general news source, misses the major point it should have taken from the study and passed on to its readers. The policy debate its readers are engaged in isn’t over older sexually active women rushing to get the vaccine. It is over the mandates for children, who are largely HPV 16 and 18 negative.

It fails to address the support the study provides for mandating vaccination or to cite the several opinion pieces on mandating HPV vaccination that the NEJM also published.

What Bioethicists R. Alto Chara Had To Say In The NEJM

The remaining arguments to be waged on the HPV vaccine are the costs versus benefits and philosophical discussion of liberty.

On the latter debate one lawyer, writing into the NEJM, presents a fine and passionate POV for public safety. What many opponents of the attempted mandates argue is that HPV unlike other diseases children must be protected from, is only communicable through intimate contact. But the author of the Letter to the Editor, says such doesn’t appear to distinguish it enough to rise above the power of the state over public safety. The power at least, as it has been defined by previous court cases permitting mandatory vaccinations.

[An] argument against compulsory HPV vaccination contends that because the infection is not casually communicable, the traditional justifications outlined in previous judicial decisions do not apply. However, the mode of transmission is a distinction without meaningful difference, and the result is the same. Twenty million persons are currently infected with HPV; 6 million more become infected each year. The threat to the public’s health, at least with respect to vaccine-related strains, is preventable with the vaccine.

If courts are ever called on to review the appropriateness of mandating vaccination against HPV, the traditional underlying principles set forth to justify vaccine mandates could easily outweigh concerns about the mode of transmission. Courts must rely on and respect the established precedent on which immunization mandates have been built.

Maybe the argument, is for no vaccine mandates or it falls flat.