(RxWiki News) One of the only vaccines that is known to prevent some forms of cancer is the HPV vaccine. Those who might worry about its safety have no reason to fear.
A recent study found no increased risk for any medical conditions or disorders after girls got the HPV vaccine.
The HPV vaccine protects against four strains of human papillomavirus (HPV).
HPV is a sexually transmitted virus that can cause cervical cancer, throat and neck cancer and anal or penile cancer.
The researchers found no evidence that autoimmune, neurological or other conditions showed up more frequently among vaccinated girls.
The authors also found that the vaccine does not increase the risk of blood clots among girls.
"Ask your doctor about the HPV vaccine."
The study, led by Lisen Arnheim-Dahlström, of the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet in Sweden, looked for possible serious effects occurring after teen girls received the HPV vaccine.
The researchers compared almost one million Danish and Swedish girls (997,585 total), aged 10 to 17, from October 2006 to December 2010.
Of these, just under a third — 296,826 girls — had received a total of 696,420 doses of the HPV vaccine.
The researchers looked for any one of 53 different possible conditions or incidents among all the girls, both vaccinated and unvaccinated, for up to six months after the vaccinated girls received their doses.
Among these conditions were autoimmune disorders, neurological disorders, blood clots and other medical events.
For any conditions which occurred in at least five vaccinated girls, the researchers examined the risks of those conditions compared to unvaccinated girls.
In these comparisons, the researchers took into account each girl's age, country, year of receiving the vaccine, education level, socioeconomic status and parents' birth country.
A total of 29 outcomes showed up in at least five vaccinated girls, requiring a closer look.
Only three of these showed up at a higher rate among the vaccinated girls — the autoimmune conditions Behcet's syndrome, Raynaud's disease and type 1 diabetes.
However, the researchers found that the likelihood of having one of these conditions in the six months after vaccination was the same as the likelihood long after vaccination, and the events happened randomly, without a pattern linked to the vaccines.
In addition, the link for these was too weak to be related to the vaccine — it either occurred in fewer than 20 vaccinated girls, or the increased risk was not high enough, or the risk was not consistent across both countries.
The other 23 autoimmune conditions studied more closely did not occur with a higher risk in vaccinated versus nonvaccinated girls.
Neither did five neurological conditions they examined more closely. In fact, epilepsy occurred among 34 percent fewer vaccinated girls.
Finally, the researchers found no evidence of a link between the vaccine and blood clots.
"This large cohort study found no evidence supporting associations between exposure to the quadrivalent HPV vaccine and autoimmune, neurological and venous thromboembolic [blood clot] adverse events," the researchers wrote.
"Although associations for three autoimmune events were initially observed, on further assessment these were weak and not temporally over time related to vaccine exposure," they wrote.
The study was published October 9 in BMJ. The research was funded by the Swedish Foundation for Strategic Research and the Danish Medical Research Council.
Two authors have received past research funding from GlaxoSmithKline, Sanofi Pasteur MSD and Merck. No other possible conflicts of interest were reported.