Monitoring polio supplementary immunization activities using an automated short text messaging system in Karachi, Pakistan

Problem Polio remains endemic in many areas of Pakistan, including large urban centres such as Karachi.

Approach During each of seven supplementary immunization activities against polio in Karachi, mobile phone numbers of the caregivers of a random sample of eligible children were obtained. A computer-based system was developed to send two questions – as short message service (SMS) texts – automatically to each number after the immunization activity: “Did the vaccinator visit your house?” and “Did the enrolled child in your household receive oral polio vaccine?” Persistent non-responders were phoned directly by an investigator.

Local setting A cluster sampling technique was used to select representative samples of the caregivers of young children in Karachi in general and of such caregivers in three of the six “high-risk” districts of the city where polio cases were detected in 2011.

Relevant changes In most of the supplementary immunization activities investigated, vaccine coverages estima