Creating immunity

The argument in a CMAJ editorial1 that “Unless a large proportion (usually over 95%) of the population is vaccinated, herd immunity will not result and outbreaks will recur” had me scratching my head. The same editorial notes that “the near-complete immunization of whole populations in childhood has led, decades later, to whole populations of adults with waning immunity to some childhood diseases,” giving as an example pertussis, which “is now as common among adults as among children.” This is not the first time that the efficacy of vaccines has been called into question.

“Herd immunity” was defined in the first half of the last century as protection of any given population from a transmissible disease, through lifelong or long-term immunity caused by contraction of and recovery from the disease;2 immunity related to high standards of nutrition, cleanliness and sanitation was a cofactor.3 As the case of pertussis and other examples show, herd immunity through vaccination is a flawed concept. For various reasons, the efficacy of vaccines is highly variable (and never complete), and any immunity derived from vaccines is only short-lived.4

It wouldn't be so bad if all we had to worry about was lack of efficacy — after all, we managed to survive for thousands of years with no vaccinations. However, the fact that these agents of dubious effect are also harmful is another matter. However, recent data from the US Vaccine Adverse Event Reporting System show that deaths following pertussis vaccine far surpass deaths from pertussis (20 deaths yearly from the disease, 57 following vaccinations, which is a gross understatement because only 10% of reactions — at most — are reported).2

I agree that we need national leadership on vaccination policy and a much improved national system of recording morbidity and mortality related to specific diseases. Much more pressing is the need for an adverse reaction reporting system that encompasses all possible adverse events and is easily accessed by the general public. What we don't need is multitudes of expensive new vaccines on top of the many we already have, within an already faltering health care system.

Susan Fletcher Vaccination Risk Awareness Network Inc. Sechelt, BC