[Measles and Rubella IgG Seropositivity in the Post-elimination Era, Costa Rica, 2012-2023Soropositividade de IgG para os vírus do sarampo e da rubéola na era pós-eliminação, Costa Rica, 2012-2023].

Objective: To determine measles and rubella IgG seropositivity in the post-elimination era, based on data generated by the Costa Rican National Reference Center for Virology laboratory at Inciensa from 2012 to 2023. Methods: Cross-sectional, descriptive, observational study analyzing the frequency of measles IgG and rubella IgG reactivity by enzyme-linked immunofluorescence (ELISA) in 877 subjects. Results: The average age of the studied individuals was 36 years; 51.8% were women. Measles and rubella IgG seropositivity was slightly higher in females. The average seropositivity over the study period was 74.8% for measles IgG antibodies and 84.5% for rubella. The age group 50 years and older exhibited the highest positivity for the both measles and rubella IgG, while the 20-to-39 age group had the lowest protective humoral response. Conclusions: Descriptive studies of measles and rubella IgG seropositivity can identify age groups susceptible to these infections, which in turn can guide health authorities in directing supplementary immunization campaigns to strengthen the immune response of the population and prevent outbreaks of both diseases.