A young boy receives two drops of oral polio vaccine during Ethiopia’s 1999 NIDs.

Immunization Days

Immunization days are designed to interrupt poliovirus transmission by immunizing all children under the age of 5 regardless of their immunization status. Two rounds of immunization days are held 4 to 6 weeks apart and should take place each year for at least 3 consecutive years. More rounds may be necessary, particularly in areas where routine immunization coverage is low.

Based on the epidemiological picture, immunization rounds may cover:

• All children nationwide (national immunization days, or NIDs)
• High-risk areas (subnational immunization days, or SNIDs)
• Outbreak response to eliminate last reservoirs of virus (“mopping up”)