A Natural Experiment on the Effectiveness of the HPV Vaccine

There is an interesting article in The Texas Tribune on the effects of the HPV vaccine on cervical cancer rates in Texas. Or rather, it is about how the lack of a mandate to give the HPV vaccine to the recommended groups has resulted in Texas having one of the highest rates of cervical cancer in the United States. For comparison, the author uses the experience of Australia, a country that has given free and easy access to HPV vaccination for boys and girls for quite a while now. The result in Australia has been that the country is on pace for eliminating cervical cancer soon.

The article states:

“Now, 12 years after Texas and Australia first veered onto wildly different courses regarding HPV prevention, their gap in health outcomes has widened demonstrably. Australia is on track to become the first country to eliminate cervical cancer, perhaps within a decade. Texas, meanwhile, has hardly made a dent in its rate of cervical cancer — which remains one of the highest in the United States, with an incidence comparable to that of some developing countries.”

In epidemiology, we call these kinds of situations community trials, where one entire community is given an intervention while another isn’t. We then would follow both communities and measure the expected (and unexpected) outcomes of the intervention. However, what we are observing between Texas and Australia is more of a natural experiment. In a natural experiment, you observe different populations and measure their outcomes without any kind of intervention. You just allow nature to take its course and then measure what is going on based on the natural attributes of the two populations.

An example of a natural experiment can be observing the rates of tooth decay in two communities, one where the water has naturally occurring fluoride and one where there is no measurable fluoride in the water. Or you can observe one town above the arctic circle and one in the equator and measure rates of seasonal affective disorder or skin cancer, or something you theorize is affected by the natural length of the day/night cycle.

So why is this difference in cervical cancer rates between Australia and Texas more of a natural experiment than a community trial if the vaccine is a man-made intervention and not something that happens naturally in either community? Well, the answer is that the nature of the communities is what determines whether the vaccine is mandated, not so much the availability of the vaccine. Texas’ nature is conservative, with many groups being opposed to the HPV vaccine on moral and political grounds. Australia is more liberal in the relationship of the people to their government. That is, they trust the policymakers on the best course of action to prevent a serious and sometimes deadly disease.

Back in 2007, Governor Rick Perry of Texas issued an executive order to mandate that HPV vaccination be given to the recommended groups — primarily teenage girls — as a requisite for school admission. In doing so, he set off a controversy with parents and politicians who appear to be okay with HPV infection as a result of the human experience… Or they were convinced that young girls would become promiscuous if they no longer had to fear genital warts or cervical cancer.

From the Texas Medical Association:

“The governor is correct in his assessment that cervical cancer is a preventable killer. The Texas Cancer Registry report, Cervical Cancer in Texas, 2006 , says that while cervical cancer is one of the most preventable and detectable cancers through regular screenings, an estimated 1,168 Texas women would likely be diagnosed with the disease and 390 would die from it in 2006.

Moreover, being diagnosed or dying from cervical cancer varied among Texas women by race and ethnicity. From 1999 to 2003, both Hispanic and African-American women had higher cervical cancer incidence and mortality rates than those of white women. A study by the Centers for Disease Control and Prevention found that Hispanic women, particularly those who live in counties along the United States-Mexico border, are less likely than white women to receive routine screenings for cervical cancer.

These statistics are why the HPV vaccine is needed to save Texas women’s lives, says Dallas pediatrician Molly Droge, MD, a member of the Texas Medical Association Council on Public Health.

She quickly dismisses critics’ claims that the vaccine would encourage young girls to become sexually active. On the contrary, she says, physicians now have a way to broach the topic of sexual health with young patients and their parents.

“Giving young girls this vaccine does not encourage or give them permission to become sexually active. Rather, it gives physicians and parents the opportunity to talk to them about the risks of becoming sexually active early on,” she said.

Dr. Droge acknowledges some drawbacks, the first being that the vaccine has only been on the market since June. Long-term effects are unknown, and it hasn’t been determined if boosters will be needed to keep young girls and women immunized against the virus. Yet she quickly points out these are inherent risks with any new vaccine on the market.”

The mandate was rescinded due to political, moral and religious objections and here we are, 13 years later, with a state in the United States of America with a cervical cancer rate comparable to that of some developing nations. (Many of those nations don’t have the HPV vaccine available to the general population. And the concern that the vaccine was too new? Thirteen years of evidence has shown an excellent record of safety and effectiveness.

In Australia, the vaccine was available for girls in 2007 and then boys in 2013. While there were the usual objections from anti-vaccine organizations and individuals, the vaccine was made available for free and without obstacles. Ten years later, there has been a noticeable and critical reduction of cases of genital warts, abnormal pap smears, precancerous lesions and cervical cancer.

This is even more evidence for the safety and effectiveness of the HPV vaccine (all licensed brands) and it offers a great opportunity to understand how the nature of a population’s politics and belief systems affects the population’s health. As the Tribune article states, both Texas and Australia are comparable in population size and economic measures. Unfortunately for women in Texas, the two couldn’t be more different in how they approached HPV vaccination.

Author: René F. Najera, DrPH

I am the editor of the History of Vaccines site, an online project by the College of Physicians of Philadelphia. All opinions expressed on these blog posts are not necessarily those of the College or any of my employers. Check out my professional profile on LinkedIn: https://www.linkedin.com/in/renenajera Feel free to follow me on Twitter: @EpiRen

One thought

  1. Cervical cancer is one of most common diseases among women worldwide. Human papilloma virus (HPV) is known as precursor of cervical cancer. Cervical cancer can be prevented effectively by practicing hpv vaccine. But the coverage of HPV vaccine is remain low. The objection of study was to analyze factors related to HPV vaccine pratice among adult women. https://e-journal.unair.ac.id/JBE/article/view/1299

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