A Luxurious Decision: The HPV Vaccine
I won’t forget the phone call. At the time, my brother, sister and I were engaged in an epic battle of monopoly. My mum answered the ringing phone, and when we heard the heart-wrenching sobs, we realized something was terribly wrong. I was too young to know what a cervix was, but I did know that cancer of anything was bad. My mother’s only sister would pass away in her arms, 4 years later.
Cervical cancer: so prodigious in one woman, Henrietta Lacks, that it has been proliferating for over 60 years after her death as an immortal cell line used in biomedical research. While the incidence of cervical cancer has been reduced through Pap Smear screening techniques, it remains the fourth leading cause of death by cancer (following breast, lung, and colorectal cancer) in women, globally. Out of the 1 in 150 women that are expected to develop the disease, more than 1 in 500 will die from it.
Human Papilloma Virus (HPV), the culprit of nearly all cases of cervical cancer, has many faces. There are over a hundred ‘types’ of the virus, 40 of which can be sexually transmitted. Estimates suggest over 70% of sexually active Canadians will have a sexually transmitted HPV infection at some point in their lives. Two of these types (HPV-16 and HPV-18) are particularly high risk in their ability to cause cancer: they are responsible for over two thirds of cervical cancer, the vast majority of anal cancers, and one in three cases of eosophageal and penile cancers. There is no cure for HPV infection, only treatment of the physical symptoms of infection, namely precancerous and cancerous lesions. In the case of HPV, prevention is indeed the best medicine. Such preventative measures were first licensed for use in 2006, over ten years after my aunt’s diagnosis.
There are two licensed prophylactic vaccines available: both Cervarix and Gardasil offer protection from the most high-risk types of HPV. Gardasil has the added benefit of being licensed for use in both males and females, and offers protection against HPV types 6 and 11, the major cause of genital warts. To make these vaccines, yeast are engineered to produce massive amounts of virus proteins: the same proteins that make up the empty shell (capsid) of the virus. Because only these proteins, not virus DNA, are purified for use in the vaccine, there is no risk of infection. These proteins are introduced into the human body through intramuscular injections. After 3 doses over a 6-month period, specific and long-lived antibodies are generated against these harmless proteins. If the real virus rears its head, the body’s antibodies immediately recognize the same virus capsid proteins, and mounts the most efficient and effective immune response possible.
My aunt was scheduled to begin treatments about 4 months after her initial diagnosis, however that schedule was accelerated after she hemorrhaged on her kitchen floor. She lost nine pints of blood that day, and flat-lined en route to the hospital. She survived, and was given radiation treatment that consisted of radioactive material sewn nearby the tumor. Her doctor’s described this as her “life insurance policy". After several rounds of chemotherapy, the cancer had gone into remission.
Two years later: in the kitchen, the remnants of the Christmas turkey were being carved away for soup. Once my grandfather pried the wishbone free from the carcass, I was the lucky grandchild selected to hold on the opposite end and make a wish. I still remember the childish disappointment I felt when I my end snapped only a few centimeters above my fingers. And I still feel the shame of my (now forgotten) childish wish when my grandfather, once prompted to share, quietly said he wished his eldest daughter would survive. It was discovered several months earlier that the life insurance policy had failed. The cancer had returned, and she would never recover.
As the data rolls in, comparisons between pre-and post-vaccine rates of HPV reveal that the vaccine is a success. Markowitz and colleagues report in the Journal of Infectious Diseases that the prevalence of the most high-risk types of HPV was significantly reduced in girls aged 14-19 once HPV vaccines were introduced into routine immunization schedules in late 2006. Prior to routine HPV vaccination, between 2003-2006, 1 in 10 women were HPV positive for high-risk strains. Post-vaccination, that number has fallen to 1 in 20.
One of the most contentious issues surrounding the HPV vaccine is timing. The reality is, vaccination before or at the onset of puberty is critical for protection for three main reasons. First, for a protective strategy to be effective, it needs to be in place when the risk is greatest, and the risk of contracting HPV is highest within 5-10 years of a first sexual experience. Second, benefits of vaccination are greatest in children aged 9-15: the virus-killing antibodies generated in this age group are over twice as high compared to 15-26 year-olds. After the age of 26, clinical trials demonstrates limited, if any, protection is offered to women. And third, these vaccines are not effective as a treatment, as the virus-killing antibodies induced by vaccination are not found in the epithelial cells where the cancer lives. So once HPV is established, no amount of vaccine-induced antibodies will eliminate the virus.
I try to understand the discomfort of parents who are asked to consider vaccinating their children against a sexually transmitted infection. Such vaccinations are as close as parents can get to making informed sexually educated decisions for their children. One thing is for certain: the discomfort of such a decision is a luxury, one that wasn’t afforded to my parents, or my grandparents. And hindsight being what it is, had such measures been available to my grandparents, my mother might be one sister richer today.
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Ammendum: Canada has a publicly funded HPV immunization strategy in place, that varies from province to province. To date, Alberta and Prince Edward Island offer the HPV vaccine to both boys and girls, which makes an awful lot of sense.
