Sir

In their Commentary article “A global call for new polio vaccines” (Nature 434, 699; 2005), David L. Heymann, Roland W. Sutter and R. Bruce Aylward argued for vaccines to be developed and stockpiled. I propose, instead, that there is no need for new polio vaccines, but rather that more sensible and coordinated use is needed of the two major vaccines in existence.

One of these is the inactivated Salk vaccine and the other the live, but attenuated, Sabin vaccine (also known as oral polio vaccine). The Salk vaccine is safe, and was used to eradicate polio in Sweden. The Sabin vaccine is not so safe: for many years in the United States most of the polio cases that did occur were shown to have originated from the Sabin vaccine, owing to reversion of the attenuated viruses.

At the time both vaccines were introduced (a little over 50 years ago), I was an employee of the Lilly Research Laboratories of Eli Lilly and was intimately involved in production of the material for Salk's clinical trial.

Even in those days, I could not understand why a decision was never made, from a public health viewpoint, to insist that all populations slated for vaccination should receive one or possibly two shots of the inactivated Salk vaccine before receiving the live Sabin vaccine. The live vaccine has the advantage of multiplying in the gut, the normal site of polio multiplication, and thus triggering a greater reaction by the host's immune system. This normal intestinal route of infection was one reason swimming pools were considered to be such a hazard. However, if the host had first been protected by the Salk vaccine the risk posed by the Sabin dose would be reduced.

I still believe that this is more sensible from a public health viewpoint and, today, one no longer has to be concerned about the animosity between the vaccine developers or manufacturers.