The Logic of the Polio Vaccine

The polio vaccine was, in evolutionary terms, a relatively modest intervention: it trained the human immune system to recognize and destroy a specific virus. The body already possessed the machinery for this recognition; the vaccine simply provided the instructions in advance. It did not add anything to the human organism that was not already there in potential. It amplified an existing capacity. This distinction — amplification of existing capacity rather than substitution for it — became the template for Salk's thinking about every subsequent form of human amplification. The vaccine worked with the immune system, not instead of it. It required a healthy organism to receive it. A body with a severely compromised immune system could not use the vaccine effectively. The amplifier was only as good as the signal it amplified.