Human papillomavirus (HPV) is the most common sexually transmitted disease worldwide, impacting approximately 79 million sexually active people, according to the latest figures from the CDC.
Linda Lévesque, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, notes that taking the quadrivalent human papillomavirus (HPV4) vaccination has been shown to combat HPV and is effective at protecting against 90% of the strains that cause cervical and anal cancer.
“Yet despite studies that have shown the safety of the vaccine, there have been some concerns about a possible link to autoimmune disorders,” she says.
In light of these concerns, a study was conducted looking at autoimmune conditions such as lupus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis.
“The reason we wanted to do this study is that parents continue to be concerned about the safety of the HPV vaccine,” says Erin Y. Liu, a study author and PhD Epidemiology student at McGill University. “It’s reasonable, considering cases of autoimmune diseases have been reported after vaccination. But, without a research study, it’s hard to know if these cases were caused by a vaccine or due to coincidental timing given the rates of these disorders in this adolescent populationt.”
Moreover, the motivation of the study was to provide scientific evidence using rigorous methods to answer the public health questions and hopefully provide parents and decision makers with the information they need when it comes to using this vaccine.
The study, published in the Canadian Medical Association Journal, showed there was no increased risk of autoimmune disorders in girls who received the HPV4 vaccination, adding to the body of evidence for the safety of the vaccine.
“The key message is that we did not find a link between HPV4 vaccine and autoimmune disorders, and this finding is consistent with the results of other studies, and we hope that these results will reassure parents and health care providers,” Liu says. “We used a large sample so our results directly apply to the girls who are currently receiving this particular vaccine.”
The study entailed utilizing population-based databases for 290,939 girls between 12 to 17 years old in Ontario who were eligible for the HPV4vaccination between 2007 and 2013. Of this study group, 180,819 girls received the vaccination in school-based clinics, with 681 diagnosed cases of autoimmune disorders between one week and two months after vaccination.
“This rate is consistent with the general rate of diagnosed cases in this age group,” Liu says. “If there is a potential association, we would have seen a higher rate of autoimmune disorder occurring in that two-month period. However, our analysis shows there was no difference.”
This was the third-largest study denouncing a link between HPV vaccination and autoimmune disorders, after two Danish studies that had a data population of nearly a million. For that reason, the study authors were not surprised by their results.
“We know that autoimmune disorders typically occur after a natural infection so biologically its plausible that vaccines could do the same thing,” Lévesque says. “At the same time, we know that this vaccine is not a live virus; in fact, it’s just a replication of the virus done through RNA technology so the body is fooled into thinking it’s been exposed to the true virus, but it has not. Our findings add to the body of evidence on the safety of the HPV4 vaccine and should reassure parents and health care providers.”
Autoimmune diseases were the only safety end point that the researchers looked at.