Most of us have heard that vaccines are one of the greatest medical advancements of modern history.  It has been touted that vaccines have prevented more deaths in the last 50 years than any other advancement.  Where does this information come from? More importantly, is it true? 

 

The eradication of Polio is often the first example people use when discussing how essential vaccines are.  Although, in the package insert for the Inactivated Polio Vaccine it states, "Prior to the introduction of inactivated poliovirus vaccines in 1955, large outbreaks of 5 poliomyelitis occurred each year in the United States (US). The annual incidence of paralytic 6 disease of 11.4 cases/100,000 population declined to 0.5 cases by the time oral poliovirus vaccine 7 (OPV) was introduced in 1961", 

 

Polio peaked in 1952 with 57,879 cases and 3,145 deaths. In 1954 the number of polio cases dropped to 38,476 with 1,368 deaths.  In two years polio cases dropped by 40% and deaths were down 78%.  The following year a vaccine became available.

 

One question that comes to mind for me is the question of correlation vs causation.  We hear it all of the time when someone is injured after vaccination, "Correlation doesn't equal causation".  So why is it that when its an adverse event we cannot determine causation, but when it is eradication of a disease we can?  Is it possible that there could have been other factors contributing to the eradication of wild type poliovirus?  What about other diseases that have seen dramatic declines?