The number of oral polio vaccine doses depends on the context where the child lives. Four doses from birth to 14 weeks of age is the recommended schedule. However, in environments such as Pakistan where the sanitation is poor and immunity response from children is weak due to chronic illness or malnutrition they should be immunized as many times as possible within four weeks every dose. In the case of a child with diarrhea, which highly prevalent in Pakistan, when receiving OPV this dose should be repeated within two weeks. As long as the coverage is low it is important to also consider the positivity of the environment for the virus.