A new method for imputing country-level estimates of hepatitis A virus endemicity levels in the Eastern Mediterranean region.

BACKGROUND

Few country-level estimates for hepatitis A virus (HAV) seroprevlance are available for the 23 countries in the Eastern Mediterranean region (EMRO) of the World Health Organization.

METHODS

We used a three-stage approach to assign an HAV endemicity level to each country in North Africa and the Middle East based on the age at midpoint of population immunity. First, we conducted a systematic review to identify all age-seroprevalence studies conducted within the past 10 years. Second, for countries without first-stage evidence we searched for incidence data and older seroprevalence data. Third, for countries with no hepatitis A data, we estimated HAV endemicity based on socioeconomic and water indicators.

RESULTS

This three-stage method allowed us to estimate country-specific endemicity levels for every country in EMRO even though first-stage evidence was only available for nine countries and for three countries only third-stage evidence was available. The region has a heterogeneous hepatitis A risk profile, with 13 countries having very high endemicity (an age at midpoint of population immunity in early childhood), three having high endemicity (late childhood), and seven having intermediate endemicity (early adulthood).

CONCLUSIONS

The three-stage estimation approach enables the creation of a complete country-level map of HAV risk in EMRO. Given the heterogeneity of HAV endemicity levels in the region and the likelihood of transitions to lower incidence rates and greater adult susceptibility in the near future, enhanced surveillance for hepatitis A would strengthen decisions about vaccination policy in the region.