For the last decade, doctors have been recommending vaccinations to girls (and now boys, too) to help protect against HPV (human papillomavirus). And for good reason — it is estimated that over 70 per cent of sexually active Canadians will contract HPV at one point in their life, with the highest prevalence concentrated among people aged 20 to 24. Its most virulent strains could lead to a number of cancers, including cervical, vaginal, vulvar, anal, penile, throat and mouth.
It’s referred to as the most common STI, although it’s impossible to track its numbers.
Unlike the top three STIs in Canada — chlamydia, gonorrhea and syphilis — which we know are steadily on the rise, HPV is not a reportable infectious disease, which is why it’s impossible to know exactly how many people are infected. The reason for this is that many HPV infections don’t show any signs and can be cleared by the body in one to two years, making it difficult to detect yet easy to spread.
“HPV is not being surveyed because most of the time, people don’t know they have it and wouldn’t think to get tested regularly for it so there wouldn’t be a sense to track those numbers,” says Frédérique Chabot, health information officer at Action Canada for Sexual Health & Rights. “What the public health system does track are the high-risk strains that have turned into pre-cancerous lesions and cancers.”
HPV comprises more than 100 strains, some of which have been directly linked to its outcomes — types 6 and 11 cause 90 per cent of genital warts, and types 16 and 18 cause 70 per cent of cervical cancer cases.
Unfortunately, unlike other STIs, condoms and dental dams don’t protect against it (although they do reduce the risk of contracting it). Transmission happens through skin-to-skin contact (including vaginal, anal and oral sex or contact), as well as through bodily fluids or mucous membranes, and its incubation period is difficult to determine since it’s hard to know when a person contracted it or how long they’ve had it. Estimates on the appearance of its symptoms range from two weeks to several months after contact.
But there is some good news: in many cases, the body can clear itself of the virus within one to two years without ever exhibiting symptoms.
If it doesn’t, however, the results can be dangerous.
“Our conservative estimate is that there are roughly 4,000 HPV-related cancers diagnosed in Canada every year,” says Dr. Rob Dmytryshyn, medical director of the Bay Centre for Birth Control at Women’s College Hospital in Toronto. “Of these, there are 1,200 deaths: one-third are due to cervical cancer and two-thirds are from other cancers.”
How has the vaccine helped?
Currently, there are three vaccines that protect against HPV: Gardasil 4, which was introduced in 2006, and protects against types 6, 11, 16 and 18; Cervarix, authorized for use in Canada in 2010, protects against types 16 and 18 (the cancer-causing strains); Gardasil 9, which was approved in 2015, and protects against additional strains as well as anogenital cancers, pre-cancerous lesions and warts. Both Gardasil vaccines are approved for females aged nine to 45, and males aged nine to 26. (Cervarix is not approved for males.)
The vaccination rates in Canada vary widely, from 40 per cent of children in the Northwest Territories to 91 per cent in Newfoundland, and many government programs have begun extending the vaccination to boys. However, it’s difficult to measure how successful it has been in terms of prevention.
“One of the challenges with HPV is that it can cause a number of outcomes, but the period between infection and specific cancer-related outcomes is long,” says Dr. Shelley Deeks, Public Health Ontario’s chief of communicable diseases, emergency preparedness and response. “It’s going to take a lot of time to determine how successful the vaccination programs have been for prevention of cervical cancer. But a number of studies have looked at the outcomes of genital warts and they’ve seen a decrease.”
Regardless, some experts are willing to draw an anecdotal correlation now.
“This vaccine has had a significant impact in reducing a lot of the cancers,” says Dr. Johnmark Opondo, deputy medical health officer with the Saskatoon Health Region. “Cervical cancer used to be the second most common cancer in women after breast cancer, but with the pap screening program and the addition of the vaccine, cervical cancers have reduced to countable numbers.”
The Canadian Cancer Society estimates that there will be 1,550 new cases of cervical cancer diagnosed in 2017, and an estimated 400 women will die from it. Aside from the HPV vaccine, the only other way to screen for cervical cancer is with regular pap tests — and those aren’t always easy to get.
“The majority of people who die from cervical cancer did not receive a pap test in the recommended time frame,” Chabot says. “It’s important to be mindful of that gap. Who falls through the cracks?”
She points out that a number of factors can come into play that will prevent a woman from receiving a pap test, including lack of a family doctor, moving and not having access to health care, living under the poverty line and socioeconomic status. There are also those who are reluctant to have an internal procedure, including women who have suffered personal trauma.
“We know in Canada there’s an issue with access to health care for Indigenous populations. Any preventative tools would help,” she says.
According to a 2015 study published in the journal Current Oncology, cancer rates among Indigenous populations, which was traditionally lower than non-Indigenous ones, had started to see a dramatic rise. While the study notes there was a 14 per cent decrease in cancer deaths between 1991 and 2004, racial and ethnic minorities continued to die at disproportionate rates. It also noted that HPV was more prevalent among Indigenous women (30 per cent in 2008).
“Compared with other Canadian women, aboriginal women have a cervical cancer prevalence that is higher by up to a factor of three and a cervical cancer mortality rate that is higher by up to a factor of four,” the study authors noted.
The vaccine has received backlash (but it’s unfounded)
Yet, studies continue to pop up questioning the safety of the HPV vaccines, although they are often misinterpreted and misquoted.
In September 2016, the WHO published a paper on their website that seemingly drew a correlation between girls who had received an HPV vaccination and negative health outcomes, including chronic fatigue syndrome, complex regional pain syndrome (CRPS) and postural orthostatic tachycardia syndrome (POTS). Another study published by the American College of Pediatricians in January 2016 found a possible link between the vaccine (specifically Gardasil) and premature ovarian failure (or premature menopause).
The WHO study was led by Dr. Rebecca Chandler, a research physician at the Uppsala Monitoring Centre, a WHO collaborating body for drug monitoring, and it looked at reported adverse effects from girls in Japan and Denmark. But before anyone jumps to conclusions about discrediting the vaccine, she says, these studies only serve as a hypothetical generalization of analysis — there’s no way of knowing how many people were vaccinated versus how many people reported adverse reactions.
By analyzing the cases and arranging them to find patterns, she noted that POTS (which causes headaches, fatigue and dizziness) was more prevalent in Denmark, and CRPS popped up more in Japan.
The reasons why are not clear, however.
Similarly, Dr. Scott Field, who authored the American College of Pediatricians report, says the possible link between Gardasil and premature menopause was based on two small case series, and there’s no way of knowing for sure that this particular vaccine was to blame.
The Children’s Hospital of Philadelphia notes that polysorbate 80 is a stabilizer that is also used in ice cream to prevent melting. It states that there is no link to infertility.
Unfortunately, some of the misinformation about the vaccine has led to an international decline in vaccination rates. Chandler says only 20 per cent of school-aged kids in Denmark received the vaccine in 2016 compared to 90 per cent five years ago; less than three per cent got it in Japan; and Ireland reported a 50 per cent vaccination rate last year compared with 80 per cent two years prior. There were no policy changes or warnings about the vaccine in those countries.
“The large majority of people are declining it but only a small fraction would probably be at risk,” she says. “I believe we have the scientific capability to identify if it’s a risk and we can characterize it.” Which means the individual potential outcomes — POTS, CRPS and chronic fatigue syndrome — need to be studied and compared with standard epidemiological studies.
“From the data coming in, we have no reason but to expect that the vaccine will do what it’s meant to do, and we already know it has had some effect on genital warts,” she says. “It would be a tragedy to stop taking it.”
Read more from our series Below the Belt: Canada’s STI Problem.