The following is from a 2011 online article, “Ten Vaccine Myths”, posted by Catherine O’Driscoll to Dogs Naturally Magazine.

Myth No. 1

Vaccines protect our dogs against disease, helping to ensure they live long, healthy, happy lives.


Vaccines only sometimes protect our dogs against disease (if at all). Scientific studies into human vaccines have shown that just as many vaccinated people, and sometimes more vaccinated people, contract diseases as do unvaccinated people.

A study conducted by Canine Health Concern during 1997, involving 2,700 dogs, showed that 68.2% of dogs in the survey with parvovirus contracted it within three months of being vaccinated. Similarly, 55.6% of dogs with distemper contracted it within three months of vaccination; 63.6% contracted hepatitis within three months of vaccination; 50% contracted parainfluenza within three months of vaccination; and every single dog with leptospirosis contracted it within that three month timeframe.

So vaccines represent – at best – only a 50/50 chance of protection.

Needless to say, this “study” did not involve the controlled exposure of 2,700 dogs (or 4,000, the number used on the author’s website) to diseases ranging from parvo to influenza within the three months following their respective vaccinations. Nor did it demonstrate that any vaccine is at best 50% effective.

Canine Health Concern, founded by the author of the article, evidently conducted a survey, and while the details are not easily accessible (or worth looking too hard for, I think), one may assume some fraction of surveyed pet owners happened to own dogs afflicted (either past or present) by various diseases. Suppose 22 dogs (out of the either 2,700 or 4,000 whose owners were surveyed) suffered parvo infection, and 15 of those happened to contract it within three months of being vaccinated. Voila, you have your 68.2%.

Never mind if 100 or 1,000 other vaccinated dogs were in fact vaccinated, exposed, and protected. No matter if the survey respondents either lied or were confused regarding their pets’ vaccination status. No matter if the vaccines in question were expired or faulty. No matter if the relevant sample is in fact so tiny that drawing conclusions is unwarranted.

I normally try to avoid such low-hanging fruit, but O’Driscoll’s aggressive promotion of junk science (and personal abuse of math) is too egregious to ignore.

© Ruth Crisler and Spot Check, 2012.