A cornerstone of the polio eradication strategy is the need to ensure high (more than 80%) immunization coverage of children in the first year of life, with at least three doses of oral polio vaccine as part of national routine immunization schedules.
While routine immunization alone cannot eradicate the disease, good routine oral polio vaccine coverage increases population immunity, reduces the incidence of polio and makes eradication feasible.
If uniformly high immunization coverage is not maintained, pockets of non-immunized children build up, favouring continued spread and outbreaks of the poliovirus.
According to WHO/UNICEF immunization coverage estimates, 86% of infants received three doses of oral polio vaccine in 2010, compared with 75% in 1990.
Polio-free countries must continue to ensure high levels of immunization coverage to prevent the re-establishment of poliovirus through importations from other countries. This can happen through international travellers, migrant populations or population sub-groups who refuse immunization.
An increasing number of industrialized, polio-free countries are using inactivated polio vaccine (IPV) in routine immunization schedules. IPV is not recommended for routine use in polio-endemic countries or in developing countries at risk of poliovirus importations as it does not stop transmission of the virus, and is more complex to administer and costly than oral polio vaccine.