A study on measles immunity among pregnant women in Sri Lanka, conducted concurrently with the country’s efforts to eliminate the disease

Introduction: Indigenous transmission of measles was eliminated in Sri Lanka in 2019, but a resurgence has been observed recently. High population immunity is considered to be the key element in sustaining the elimination status. Measles seroprevalence data in Sri Lanka are sparse. As pregnant women and neonates are two groups who would experience the most detrimental complications of measles, data on it is important to ascertain maternal immunity. The objective of this study was therefore to determine measles IgG seroprevalence among a selected group of pregnant mothers and to determine factors associated with seropositivity.Methodology: A descriptive cross-sectional study was conducted at antenatal clinics of a leading tertiary care maternity hospital in Colombo, Sri Lanka. Testing for measles IgG was carried out at the Department of Microbiology, Faculty of Medicine, University of Colombo Sri Lanka. Sociodemographic data was collected. Measles-specific IgG was determined using a validated commercial assay (AccuDiag™ measles IgG quantitative ELISA).Results: Of 391 participants, measles IgG was positive in 91.3% (95% CI 89.5-95.0%). Eleven (2.8%) had equivocal results. The geometric mean titre was 0.48 IU/ml (SD 0.28). Seropositivity fell from 100% in the oldest age group (41-45 years) to 71.4% in the youngest age group (15-19 years). No difference in the mean antibody titre was observed among age groups. Having ≥4 household members during childhood was the only other factor significantly associated with seropositivity apart from age.Conclusions: Immunity against measles was high among the study population. However, the younger age groups had a higher susceptibility.