Vaccine: X · Published 2026-07-16 · DOI 10.1016/j.jvacx.2026.100879
Fausta S. Michael, Stephen E. Mshana, Kelvin Tenga, Gerald Misinzo, Mariam M. Mirambo
Background: Interruption of measles virus transmission requires sustained population immunity of ≥95%. This study assessed measles immunoglobulin G (IgG) seropositivity and antibody levels among measles IgM-negative children during the 2022–2024 measles outbreaks in Tanzania. Methods: A total of 526 measles IgM-negative samples were analyzed using a quantitative measles IgG enzyme-linked immunosorbent assay. Seropositivity was defined as an IgG concentration ≥200 mIU/mL. Data were analyzed using STATA version 15. Results: Overall measles IgG seropositivity rate was 82.7% (95% CI: 79.4–85.9). Seropositivity was similar among children who received two doses of measles-containing vaccine (MCV) (83.6%) and those who received one dose (82.1%). Seropositivity rates did not differ significantly across age groups (1–<2 years: 83.7%, 2–4 years: 83.8%, 5–9 years: 78.1%, and 10–14 years: 83.3%; p = 0.632). However, children who received two MCV doses had significantly higher geometric mean concentrations (GMCs) of measles IgG antibodies than those who received one dose (637.8 mIU/mL [95% CI: 582.6–698.4] vs. 538.4 mIU/mL [95% CI: 506.0–571.8]; p = 0.002). GMCs were higher among children vaccinated at 9 months than among those vaccinated later (616.0 mIU/mL [95% CI: 570.8–665.6] vs. 539.0 mIU/mL [95% CI: 503.4–577.2]; p = 0.008). Samples collected during the 2022 outbreak were independently associated with IgG seronegativity (aOR = 2.56, p = 0.002). Conclusion: IgG seropositivity remained below the ≥95% herd immunity threshold, indicating persistent immunity gaps among measles IgM negative children investigated during measles outbreaks. Strengthening timely uptake of two MCV doses is essential to interrupt measles transmission.
Abstract from DOAJ. Public domain (CC0 1.0).
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Michael, F., Mshana, S., Tenga, K., et al. (2026). Age-stratified measles IgG seropositivity among measles IgM-negative children aged <15 years during the 2022–2024 outbreaks in Tanzania. Vaccine: X. https://doi.org/10.1016/j.jvacx.2026.100879