What are the problems/challenges in the polio and smallpox?

Polio
Poliomyelitis or as commonly known as Polio, one of the intensely infectious disease that affects children causing paralysis and in many cases lead to death as well. This is caused by infection from any one of three types of poliovirus.
Problem
It is spread through food, water and hands that are contaminated with the faeces of someone who is infected with the virus. The person who is infected with this may or may not show any symptoms however, they still act as a source of virus. Moreover, objects like toys, bottles or even clothing that have been used by infected person can easily transmit the virus to a healthy person. People who are residing in areas with acute access to water or unhealthy hygiene conditions can be easily trapped in this machine. Essentially, problem with this disease is its rapid rate of spread that can infect many children at once. Moreover, most of the time pathogens remain dominant in the body hindering the child to comprehend the sickness.
Challenges
The vaccine of Polio is provided to all the children ranging from the age of 1 to 5 years orally also called as OPV that actually...