Reply To: Hospital Pharmacy — GBS and Vaccination: Usually Unrelated

April 7, 2012 at 6:09 pm

No, i am not employed by any government agency or pharmaceutical company. I am retired and not employed by anyone, and have never been employed in any aspect of medicine. I am an engineer.

It is not possible to say what illnesses a person would have contracted, had their past experiences been different. It is likewise not possible to say with certainty what caused any particular case of GBS or CIDP — there is no test for it — although there is a strong association with infection by campylobacter jejuni, so it is reasonable to infer causality when that pathogen is known to have been present.

In the case of influenza, the connection is much less clear. There are a few thousand cases of GBS in the US each year, and many millions of doses of influenza vaccine administered each year, so many people who acquire GBS in any given year will have been vaccinated. Some of those cases of GBS will coincide in time with vaccination purely through chance — temporal coincidence is not proof of causality — so studies looking for a link between GBS and vaccination must determine whether the incidence is significantly different than that expected by chance.

The possibility of a link between influenza, influenza vaccine, and GBS is looked at every year by health agencies in several countries. All studies, with the sole exception of those for the 1976 H1N1 vaccine in certain populations, give similar results: there is no significant difference in incidence of GBS between those who have been vaccinated for influenza and those who have not. If there is a causal relationship between an influenza vaccine and GBS, it is on the order of about one case per million vaccinations over what is expected by chance alone. You don’t have to take my word for this; I have posted links to several studies in this forum.

So there are two possibilities which must be considered:

1. There may be no causal relationship at all, as this is consistent with the incidence being the same for those vaccinated and those not vaccinated.

2. There may be a causal relationship. This requires further explanation of two facts: first, that the vast majority of those vaccinated do not develop GBS; second, that those who are not vaccinated develop GBS at the same rate as those who are.

Hypothesis two can be explained in this way: A very small segment of the population are susceptible to acquiring GBS from some strains of influenza, for reasons that are not known. Such persons may acquire GBS either from infection from the influenza virus or from a vaccine derived from the virus.

If you have another explanation which supports hypothesis two, I invite you to state it.

Despite the statistics, most people who develop GBS within a few weeks of receiving a vaccination will believe the vaccine caused it, whether that is true or not. This is understandable and harmless in itself, however there is a great potential for harm in other people concluding that, because some people (supposedly) have been harmed by a vaccine, therefore they should not be vaccinated or have their children vaccinated. This is an invalid and dangerous conclusion, yet some people reach it. Examples can be found in the older threads on this website. This has led to a decline in childhood vaccination in the US, to a resurgence in childhood diseases which were nearly eradicated by vaccination, such as Pertussis, and increased childhood mortality.

So to sum up, believe what you like about the cause of your own case — it doesn’t matter — but misinformation about the safety of vaccination generally will get an argument from me.

Respectfully, GH