The vaccination against polio has played a great role towards the achievement of the eradication of polio. The vaccine is available both in the injectable as well as the oral form. The oral vaccine is the one currently in use in India. Western countries have switched to the injectable form of the vaccine. The comparison between the two is outlined in the table below. The injectable vaccine is called Salk vaccine and the oral form is called Sabin vaccine.

Injectable vaccine	OPV
1. Contains killed virus.	Live attenuated (cannot cause polio but stimulates immunity) virus.
2. Given subcutaneously or IM.	Given orally.
3. Does not produce immunity in the intestinal tract.	Does produce immunity in the intestinal tract.
4. Vaccine is more expensive.	Cost wise less expensive.
5. Not useful in controlling epidemics.	Can be effectively used in controlling epidemics. Even a single dose elicits substantial immunity (except in tropical countries).
6. Does not require stringent conditions during storage and transportation. Has a longer shelf life.	Needs to be stored and transported at sub–zero temperatures, unless stabilized.

The dose schedule for the oral polio vaccine
The vaccine should be administered with a dropper. This is the most direct and effective way to deliver the correct drop size. Administering with a spoon is not recommended. Three drops of the vaccine should be instilled into the child’s mouth. Since the failure rate of the vaccine has gone up in recent years (up to 30% in some communities), the current recommendation is to give five doses of the vaccine to ensure adequate protection.

Contraindications for use of the oral polio vaccine
Since the oral polio vaccine contains live viruses, it should not be given to people whose immune system is compromised. For e.g. people with malignancies, those who are on chemo or radiotherapy, on steroids, or those who have some immuno deficiency disorders. It should also not be given to those children who have an ongoing acute infection such as diarrhea, dysentery etc.

In contrast, since the injectable form of the virus contains inactivated viruses, there is no risk of flare up of disease and the vaccine can safely given to patients whose immune system is compromised.