Mini-Science Q & A – Vaccines: panaceas or poisons?

Mini-Science logo At the conclusion of each Mini-Science lecture, audience members submit their questions to the evening’s presenter, who answers as many as possible on the spot. Three of the unanswered questions are sent to the presenter for posting here. Here are questions from Dr. Brian Ward’s lecture “Vaccines: panaceas or poisons?” (April 28, 2010).

Q: Polio can recur in some people who had the disease without paralysis. Is vaccination an option for these people?

A: Vaccine-strain polio can persist in the intestines of some people with abnormal immune systems for many weeks-months. Even though the virus can sometimes mutate to become neurovirulent (i.e., able to attack the nervous system more easily), I’m not aware of really late cases of paralytic disease in such chronic shedders. It is likely that wild-type poliovirus can also persist for prolonged periods in the guts of some people but I am not aware of any studies that show this directly. Whether or not poliovirus persists in people who develop ‘post-polio syndrome’ (PPS) has been debated for many years but the available data are not consistent. Most virologists and neurologists currently believe that viral persistence is not required for the development of PPS. Most individuals who have had paralytic disease or who develop PPS have relatively high antibody levels against polio… so vaccination would be unlikely to be of any benefit.

Q: How soon after a vaccination does VAERS ‘consider’ a link to an autoimmune event, for example pediatric Type 1 diabetes?

[Blog editor’s note: VAERS is the Vaccine Adverse Event Reporting System, a United States program which collects information about adverse events that occur after administration of vaccines. The Canadian counterpart is CAEFISS, the Canadian Adverse Events Following Immunization Surveillance System.]

A: I’m not entirely certain what is being asked … so I will answer in two ways:

  1. I don’t think that the VAERS system (or any other passive reporting system) puts any arbitrary time limit on a report. If someone wishes to report an event occurring 2 minutes or 2 years after a vaccine, it is my understanding that this report will be entered into the system. This lack of ‘filtration’ is both a strength and weakness of these kinds of systems. On the positive side, there is no barrier to reporting. On the negative side, if no one ever enters type 1 diabetes as a possible vaccine-associated event, the VAERS system will never flag it for consideration.
  2. If a new vaccination program is started and there is suddenly a ‘bump’ in the reporting of ANY serious adverse event associated with vaccination, both the US and Canadian passive surveillance systems would probably pick it up relatively quickly. However, this statement presumes both that people will report the event and that it will occur at a high enough frequency to create a ‘bump’. The more unusual the event (e.g., hair falling out), the more likely it will be recognized. The longer the lag time between vaccination and the development of such an event however, the less likely it is to be reported and picked up.

Q: My GP said that the shingles vaccine has not been tested enough yet. True or False?

A: The vaccine has been used in many thousands of people and has been licensed in both the USA and Canada (suggesting that our respective federal regulatory bodies are convinced of its efficacy and safety). I am certainly convinced of its efficacy (~60% across the board as I noted in my talk) and have recommended it to family, friends and patients. I would ask your GP what level of proof he/she requires?

Please visit the Mini-Science website for more information about the lecture series.

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