Estimating population immunity to poliovirus in Jordan's high-risk areas

Abstract

A community-based serosurvey was conducted among children ages 6-59 to assess population immunity in Jordan's high-risk areas following the Middle East polio outbreak response. The survey was a two-stage cluster-quota sample with high risk areas as the primary sampling units. High-risk areas included border and hard-to-reach areas, and areas with a high proportion of refugees, mobile communities and/or low coverage during previous immunization campaigns. Population immunity to poliovirus was high overall. In high-risk areas, Type 1 seroprevalence = 98% (95% CI = 96, 99), Type 2 = 98% (95% CI = 96, 99) and Type 3 = 96% (95% CI = 94, 98). Seroprevalence was higher in the refugee camps: Type 1 seroprevalence = 99.6% (95% CI = 97.9, 100); Type 2: 99.6% (95% CI = 97.9, 99.9), and Type 3: 100% (95% CI = 100,100). The vigilance that the Jordan Ministry of Health has placed on locating and vaccinating high-risk populations has been successful in maintaining high population immunity and averting polio outbreaks despite the influx of refugees from Syria.

Keywords: Jordan; Poliovirus; immunization strategy; oral polio vaccine; seroprevalence.

Figure 1.

Median poliovirus Types 1, 2 and 3 antibody titers among children ages 6–59 months, by governorate-high-risk areas in Jordan, 2016. Reciprocal titers of poliovirus neutralizing antibodies ≥ 8 are considered positive. Due to the large size of the Syrian refugee population in Ramtha, Irbid governorate, it was considered as an entity similar to governorate while administratively Ramtha is part of Irbid governorate.