Discover more from Where are the numbers? by Norman Fenton and Martin Neil
Did the covid vaccine cause stiff person syndrome in Celine Dion?
How do we calculate the probability of causation?
DRAFT VERSION NOT FOR DISTRIBUTION
On 8 Dec 2022 Celine Dion announced that the serious health problems she has suffered recently were due to a rare condition called Stiff Person Syndrome (SPS) (this article by Scott McLachlan incudes relevant background information about SPS).
There was no mention of Celine’s vaccine status or the fact that SPS is a known potential adverse event after vaccination, including after the Covid-19 vaccine (Abusamra et al, 2022; Yeshokumar et al, 2021), in any of the subsequent mainstream news items - including those which purported to explain more details of SPS such as this one.
However, Celine had been a very vocal advocate for the Covid-19 vaccine as can be seen in this video from May 2021 and, given her severe deterioration since then, people like Steve Kirsch suggested that the vaccine caused her illness.
Inevitably, the mainstream media attempted to spike such rumours by, for example, claiming that her condition pre-dated the Covid-19 vaccines. But she looked healthy in the May 2021 video when she implored her fans to get vaccinated.
Steve has been a leading light in the fight to expose the dangers of covid vaccines (his surveys especially provide very powerful evidence of the dangers), but in this case his claim that there was a 99.6% probability that Celine’s condition was caused by the vaccine cannot be justified based on his own data assumptions.
Here is a screenshot of Steve’s analysis:
However, a lot more subtlety (and data) is required to enable us to conclude anything about the probability that it was the vaccine that caused Celine’s SPS. You cannot base such conclusions on the number of VAERS reports alone and certainly not just in comparison to reports of SPS with other vaccines. But let’s ignore those concerns and assume that it really is the case that it is “283 times more likely for a vaccinated person to get SPS than an unvaccinated person”.
Then we still cannot infer that it was 283 times more likely that SPS was caused by the vaccine. To do so would be making a form of the fallacy of the transposed conditional (also called the prosecutor’s fallacy).
The 99.6% probability that Steve cites is actually just our revised belief in the probability that a person was vaccinated once we know that they have been diagnosed with SPS (assuming our ‘prior’ belief is 50%). That follows from Bayes’ theorem because 283 is the so-called likelihood ratio, and to get the posterior odds, we just multiple the prior odds by the likelihood ratio. If the prior odds are evens, i.e. 1 to 1, then the posterior odds are 283 to 1 in favour of being vaccinated, which is a probability of 283 in 284, i.e. 99.6%.
So we can conclude that Celine was almost certainly vaccinated. But we kind of knew that already.
The more serious problem in Steve’s analysis is that it ignores the potentially many other risk factors that can cause SPS. While medical science has not identified exactly what triggers the tell-tale autoimmune response in the brain and spinal cord that is diagnostic of SPS, there may be other congenital or environmental factors that need to be present for a vaccine to cause it. For example, it is scientifically accepted that a misdirected immune response triggers SPS (Sarva et al, 2016). This is all covered further in (Scott’s article). So, even if it is 283 times morely likely that a vaccinated person has SPS than an unvaccinated person, it can still be the case that it is 10,000 times more likely a person with congenital factors gets SPS than a person without. And in that case it is far more likely the congenital factors and not the vaccine caused the SPS.
Ultimately, the question that we and Steve would really like to answer is the counterfactual question:
Knowing that Celine has SPS, what is the probability she would have got SPS if she had not been vaccinated?
This short video uses a completely generic example to explain why we need to answer the counterfactual question to establish probability of causality and how it is possible to do so using a method involving Bayesian networks.
However, much more data is required in this case (including about the impact of the congenital and other factors on SPS). An attempt to do this properly will be left to a follow-up more technical article. For those who cannot stomach the technical details and numbers in the above video, a lay explanation of the counterfactual argument goes as follows.
In the ‘real world’ we know that a person has been diagnosed with SPS.
We don’t know for sure if this was due to being vaccinated (we don’t even know for certain if they were vaccinated) or from some other congenital factors, or a combination of both.
However, (by Bayes) the knowledge that the person has SPS enables us to update our beliefs in both “being vaccinated” and “having the congenital factors” – both these probabilities increase.
If we know for sure that the person was vaccinated then (again by Bayes and the concept of ‘explaining away’) this makes the probability of congenital factors decrease, but it is still high (much higher than before we knew about the SPS in this person). So, in the ‘real world’ we have now learnt that this person has a higher probability of the congenital factors than an average person.
We can now use that updated information about this particular person in a counterfactual world. In that counterfactual world we can calculate the probability that the person would get SPS if they were unvaccinated.
There are also many issues around the VAERS and other reporting systems data that suggest the 283 likelihood ratio for vaccinated may not be reliable. Scott’s article covers this in depth.
Finally, a personal note from Norman: I have seen Celine live several times and have tickets for two different shows in different countries for her 2020 tour that still have not been rescheduled. I really hope that these will eventually happen and pray for her health.
(to commemorate the release of the film and song Titanic 25 years ago on 19 December 1997)
Abusamra, K., Thandampallayam, M., Lukins, D., & Sudhakar, P. (2022). Stiff Person Syndrome in a patient with atypical carcinoid tumor of the lung secondary to anti-amphiphysin antibodies: A case report and literature review. Neuroimmunology Reports, 2, 100116.
Sarva, H., Deik, A., Ullah, A., & Severt, W. L. (2016). Clinical spectrum of stiff person syndrome: a review of recent reports. Tremor and Other Hyperkinetic Movements, 6.
Yeshokumar, A. K., Sun, L. R., & Newsome, S. D. (2021). Defining the expanding clinical Spectrum of pediatric-onset stiff person syndrome. Pediatric Neurology, 114, 11-15.