HPV vaccine and Guillain–Barré syndrome
Hello Reader. Today I would like to write about the latest misinterpreted scientific information regarding HPV vaccine. I have noticed an Abstract circulating on certain anti-vax websites and being received with nothing less than rapture. The Abstract is entitled: “Gardasil: A false sense of immunity?”, and was not presented at the American Society of Clinical Oncology conference in 2010, for reasons that are unclear. The Abstract was nonetheless published in conjunction with the meeting, and purports to investigate associations between the HPV vaccine Gardasil and reports of Guillain–Barré syndrome (GBS).
There are several reasons that I chose to write about this Abstract. The first, as mentioned above, is that it is being taken as undeniable evidence of Something Bad About HPV Vaccine on several anti-vax websites. The second is that it is an excellent example of over-drawing conclusions based on faulty data. The third is that it is yet another enlightening example of people misusing the Vaccine Adverse Event Reporting System (VAERS).
The Abstract itself states that, “We found 42 incidences of Gardasil-related GBS (reported mainly by medical personnel), including pts receiving Gardasil alone (N=27).
In other words, the sample has already shrunk from 42 girls to 27, because 15 of the girls had probably received another vaccination at the same time as Gardasil. This would preclude any analysis of Gardasil and GBS for those girls. The next thing that must be clarified is that, contrary to what the authors wrote, none of the cases of GBS are actually shown to be “Gardasil-related”, especially because the authors go on to state that:
“Of the 27 incidences, 33% were complete reports”
If the math were correct, this would mean that only 9 girls had complete records, including date and type of vaccine administration; dose; and length of time between vaccine receipt and GBS symptoms appearance. Yet somehow, the authors go on to state that:
“Initial symptoms averaged 30 days post-Gardasil for these 11 cases”.
I’ll shrug off the math error for a second to make a very simple point. Of the alleged 42 original cases of GBS reported after receiving Gardasil, in reality there are only 11 confirmed, post-Gardasil cases of GBS.
The authors also miss the most important part of any type of analysis: the DENOMINATOR. In other words, how many girls received Gardasil in total? Was it 100 or 1 million? Unlike the error in the percentage calculation, this is more than just a little math mistake. Rather, this is a results-busting fatal oversight, because it utterly precludes the possibility of calculating whether the number of cases of GBS reported to VAERS was greater than, equal to, or less than what it would be in a population which had NEVER received Gardasil. Therefore, it’s a darned good thing that some groups have done the epidemiology correctly, and have shown* that there is NO ASSOCIATION between Gardasil and GBS.
None of what I have written thus far even touches on the other fatal flaw of this analysis; namely, the misuse of VAERS, which has been written about eloquently at Moms Who Vax by Karen Ernst. I really can’t add to that piece; it explains very clearly why VAERS cannot be used willy-nilly with no regard for such pesky things as denominators and medical record review.
In summary, the authors of this Abstract didn’t just over-reach with their title–they didn’t even address it. There was no analysis of immunity conferred by Gardasil. There was only smoke and mirrors and nothing of any substance whatsoever. The damage that is done by this type of work becomes clear every time an anti-vaxxer tries to use it to shore up his or her misguided belief system.
*Many thanks to Chillin’ Out Vaxin’ Relaxin All Cool, aka COVRAC, for this additional and important reference.