Cross-sectional, laboratory-based study of measles seroprevalence in Oman.

Background: Since the introduction of vaccination in Oman in 1981, measles incidence has decreased, and Oman achieved measles elimination in 2019. Measles cases in the country are currently import-related.

Aim: To understand the measles immunity profile of the Omani population and identify high-risk groups.

Methods: A total of 1990 anonymous blood samples out of 2032 samples collected from all regional referral hospitals and one private laboratory in Oman from November 2015 to January 2016 were tested for measles immunoglobulin G. We grouped the study population into 4 birth cohorts and analysed the data using SPSS version 16.0. We used the χ² to test for statistical significance and used Kruskal-Wallis test to calculate the geometric mean for each age group. P < 0.05 was considered statistically significant.

Results: The overall measles seropositivity was 84.0%. Seronegativity was significantly higher among the 15-20 years (34.0%) and 20-35 years (24.0%) age groups. There was no significant difference in seropositivity by gender and nationality. Seropositivity was 72.7% in the 1987-1996 cohort and 70.1% in the 1997-2006 cohort. The mean measles antibody level was 2318.5 IU/ml.

Conclusion: This study revealed a measles immunity gap among some age groups in Oman, indicating the need for sustained high vaccination coverage, robust surveillance, targeted vaccination campaigns, and timely outbreak response.