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HPV, HPV vaccine, vaccines

Another study shows no link between HPV vaccine and autoimmune diseases

Some critics of the HPV vaccine claim it can cause autoimmune disease and describe this as a reason for vaccine hesitancy. The specter of the “Gardasil girls.” young women with bizarre, ill-defined symptoms (often described as autoimmune or autoimmune disease-like) attributed to the HPV vaccine fills the Internet and many parents searching for information on HPV vaccine safety could easily end up with wildly incorrect information. Concern about health risks are often cited by parents as a reason to pass on the HPV vaccine.

The HPV vaccine is the most effective when started before the age of 15, so getting parents on board safety wise is imperative. If kids have to wait until the age of 18 to be vaccinated they need 3 shots instead of 2 and by that time many have already been exposed to cancer causing HPV making the vaccine less effective. Remember, 49% of boys and 39% of girls in high school have had sex and data pre HPV vaccine tells us 33% of 14-19 year old girls and 23% of 15-19 year old boys are already been infected with a cancer causing HPV strain.

A study published last year gives us even more data on HPV vaccine safety. I don’t remember it getting much (if any) press, and so I think it’s a good idea to give it a signal boost as I am still hearing a lot about HPV vaccine hestitancy. The study by Grönlund et. al. was published in the Journal of Internal Medicine and was designed to see if the HPV vaccine was associated with any new onset autoimmune disease in young women. People who already have one autoimmune disease are at higher risk of developing a second one as the same combination of genetics and environment that led to the first autoimmune disease sets you up for subsequent ones. Autoimmune diseases basically travel in packs. Also, women have higher rates than men. If the HPV vaccine triggered autoimmune diseases then surely this would be the most vulnerable population and thus the place to look for a rare event.

The study, from Sweden, is a registry based meaning the team of researchers abstracted data that was previously collected for other reasons. They identified women and girls between the ages of 10 and 30 who had at least one autoimmune disease from a national health registry and cross-referenced this data with the Swedish Voluntary Vaccination Registry and the Prescribed Drug Register to identify who had been vaccinated against HPV and who had not. They also collected demographic data to identify variables and potential confounders.

The Swedish are good medical record keepers (this investment pays off time and time again in studies) and so the researchers identified 70,265 eligible individuals, around 59,000 who had never been vaccinated against HPV and approximately 11,250 who had received at least one dose. They looked for 49 autoimmune diseases in the records. The most common autoimmune conditions in both the vaccinated and unvaccinated groups were celiac disease, psoriasis, and type 1 diabetes.

Researchers identified no increased risk of new autoimmune diseases associated with the quadrivalent HPV vaccine (the older vaccine, the new one protects against 9 strains). In fact, they found 28% fewer new autoimmune diseases among HPV vaccinated girls and women. This probably doesn’t mean the HPV vaccine reduces autoimmune diseases, but you never know. Viral infections are known triggers of autoimmune conditions. Could the stress of procedures needed to screen and treat pre-cancer play a triggering role? There may also have been selection bias, meaning the healthiest patients with autoimmune diseases self-selected for vaccination and as they were healthier they were less likely to get a second autoimmune condition and the sickest (and thus more likely to get a second autoimmune condition) were advised to decline vaccination or were not offered it in the first place. There may be other unknown factors as well.

Could this possible vaccine selection bias where only the healthiest received the vaccine mean those least likely to get a second autoimmune condition were the least likely to be vaccinated and so the most at risk group was actually under represented? The authors felt it was statistically improbable such a large effect could exist given the numbers as this effect would have to completely reverse the 28% fewer autoimmune conditions in the vaccinated group and then some. In addition, the results did not change when limiting the number of preexisting autoimmune conditions to one.

Given the relative rarity of autoimmune diseases registry data is probably the only way to shed light on any connection between HPV vaccination and autoimmune diseases. Other studies looking at autoimmune disease and HPV vaccine have been reassuring and in line with these results.

The bottom line is yet another study shows the HPV vaccine is safe.

 

 

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