Seroprevalence of measles immunoglobulin G antibodies in Bahrain: A cross-sectional study using fever and rash surveillance data (2021-2025).

OBJECTIVES

Measles remains a public health challenge despite effective vaccines; recent declines in coverage led to resurgent outbreaks worldwide. This study aims to estimate measles immunoglobulin (Ig)G seroprevalence in Bahrain's population and identify immunity gaps using serological data from the national fever and rash surveillance system.

METHODS

We analyzed fever and rash surveillance data from Bahrain (2021-2025). Suspected measles cases were tested for measles IgG antibodies. Seroprevalence was stratified by age, nationality, vaccination status, and governorate. Overall prevalence was age-adjusted, and differences in seropositivity were tested using chi-square tests.

RESULTS

Among 1280 patients, the overall seroprevalence of measles IgG was 81.6% (95% confidence interval: 79.3-83.7%). Seropositivity differed between Bahrainis and non-Bahrainis (82.6% vs 77.3%; P = 0.047). There was strong evidence of differences in seroprevalence by age (P <0.001). Seroprevalence was 10.5% among those aged less than 6 months and dropped to 4.9% among those aged 6-12 months. Adjusted for age, seroprevalence was 94.3% (95% confidence interval: 85.7-97.9%).

CONCLUSION

Bahrain's age-adjusted measles seroprevalence is within herd immunity thresholds. However, vulnerabilities exist among those aged less than 18 months and non-Bahrainis. Sustained high measles, mumps, and rubella vaccine coverage and enhanced surveillance are important in maintaining measles elimination status.