What is the efficacy of polio vaccine?
The efficacy of 3 doses of OPV in West is around 80-90% while that in temperate countries like India is only 60-70%. The reasons behind poor efficacy in temperate climate are multifocal. One is the poor cold chain maintenance. Second is the interference by other GI viral infections, which are so common in countries like India. Lastly, there could be some genetic reasons for the poor response. The efficacy goes upto 90% with 5 doses of OPV in India. Theoretically, one may require 10-15 doses of OPV to reach near 100% efficacy. That is what is achieved by pulsing for 3-5 years with 2 pulse polio doses every year as has been proved in some countries. The protective efficacy is> 95% with 3 doses of IPV.
