OPV :

OPV given at the time of birth is called zero Polio. Total 5 polio doses are given in the first year of life. Over and above that 'pulses polio' doses are administered at least twice a year (usually in winter) to all children below 5 years of age, irrespective of number and time of previous polio doses.

Additional doses of polio may be given in a particular area if a case of polio is found in that area.