Seroprevalence surveys to guide programmatic action
In recent years, three seroprevalence surveys (i.e., assessment of antibody against the poliovirus serotypes) have provided immunity profiles of young children in Egypt, Indonesia and India. The findings of each survey have provided interesting country-specific results that have led to programmatic actions, where appropriate, and provided an immunity benchmark for the eradication initiative.
In Egypt, infants 6-11 months of age with a history of ~7 doses of trivalent oral poliovirus vaccine (tOPV), yielded high seroprevalence to type 1 and 2 (>99%), and somewhat lower levels for type 3. Elimination of transmission of wild poliovirus was achieved shortly after the survey was conducted in December 2004 (1).
In Indonesia, after receipt of 4 doses of tOPV, the seroprevalence to all three poliovirus serotypes was almost 100% (2).
In Moradabad (Uttar Pradesh, India), among infants 6–12 month of age, the seroprevalence study is in the laboratory phase to determine if compromised vaccine efficacy rather than failure to vaccinate is the primary cause for the continued circulation of poliovirus in northern India. The eradication program anticipates that more seroprevalence surveys will be conducted in 2009 for programme evaluation purposes, to help assess the immunogenicity of the vaccines and to identify areas to improve programmatic action.