Seroprevalence against the measles virus after vaccination or natural infection in an adult population in Madinah, Saudi Arabia

Comparison of population-based measles-rubella immunoglobulin G antibody prevalence between 2014 and 2019 in Lao People's Democratic Republic: Impacts of the national immunization program

OBJECTIVES

We evaluated the effectiveness of the Lao People's Democratic Republic's measles-rubella immunization program using the seroprevalence from two cross-sectional surveys.

METHODS

The nationwide surveys occurred in 2014 and 2019 using a multistage cluster sampling, both requiring samples from 2184 individuals from 52 randomly selected villages. Immunoglobulin G titers, measured using enzyme-linked immunosorbent assay, were considered positive at ≥120 mIU/ml (measles) and ≥10 IU/ml (rubella). We calculated the vaccination-related reduction in the force of rubella infection and the number of congenital rubella syndrome cases averted in 2019.

RESULTS

We collected 2135 (women: 55.2%, mean age: 23.2 years) and 2001 (52.7%, 23.1 years) samples in 2014 and 2019, respectively. During 2014-2019, immunoglobulin G prevalence increased from 83.9% (95% confidence interval [CI]: 83.8-84.0) to 98.3% (97.7-98.8) for measles and from 75.4% (75.3-75.5) to 87.8% (86.4-89.2) for rubella. The most plausible reduction in the average force of rubella infection was 100% (95% CI: 28-100) since vaccination started, averting 78 (95% CI: 42-128) congenital rubella syndrome cases in 2019.

CONCLUSION

This is the first population-based study for measles and rubella at two different time points in developing countries. Measles and rubella seroprevalence increased significantly during 2014-2019, greatly exceeding the immunity thresholds for their elimination.

Rubella Humoral Immunity Among the Saudi Population of Madinah in the Western Region of Saudi Arabia

Maintaining herd immunity against the rubella virus is important for controlling the spread and recurrence of rubella. Rubella vaccination for children has been affordable in Saudi Arabia since 1982. To assess the immune response derived from vaccination, we assessed the seroprevalence against the rubella virus among the population of the Madinah region. An indirect enzyme-linked immunosorbent assay (ELISA) was used to measure anti-rubella IgG antibodies in 791 serum samples obtained from 336 (42.5%) men and 455 (57.5%) women, ranging from 14 to 49 years in age. Among all participants, 94.2% were seropositive for rubella IgG antibodies, indicating a high degree of immunization. However, 5.8% of participants were seronegative, suggesting a population of either poor vaccine responders or the potential risk of waning vaccine-induced immunity. No significant difference or association with rubella seropositivity was identified according to age, sex, or pregnancy status. The median anti-rubella IgG antibody concentrations differed significantly between age groups (p < 0.001). Although a high percentage of the tested population in Madinah demonstrated anti-rubella IgG antibody seropositivity, a notable percentage of the population were seronegative, making them susceptible to infection.