Seroprevalence of mumps before the introduction of mumps-containing vaccine in Lao PDR: results from a nationwide cross-sectional population-based survey

Objective Mumps-containing vaccine is currently not a component of the national immunization schedule in Lao People’s Democratic Republic (PDR). Mumps itself is not a notifiable disease in the country and the seroprevalence of anti-mumps immunoglobulin G (IgG) in the general population is unknown. In this study, anti-mumps IgG was measured in 2058 blood samples to evaluate population immunity in the country. Results The seroprevalence of anti-mumps IgG showed a gradual increase with increasing age, starting at 10.6% (95% CI 7.4–13.7) in participants aged 1–2 years, and almost plateaued at about 75% in individuals older than 11–12 years, though it still tended toward a small increase up to 89.6% (95% CI 86.6–92.6) in participants aged 40 years or older. Compared with the results of previous studies, this increase with increasing age is less marked and the plateau of anti-mumps seroprevalence is lower. We attribute this result mainly to the lower population density in Lao PDR.