Waning of vaccine-induced measles antibodies and population immunity gaps in the post-elimination era: a multicenter seroepidemiological study in China
TL;DR
High MCV coverage does not necessarily ensure sustained population immunity in the post-elimination era, and waning humoral immunity, delayed vaccination, and heterogeneous vaccination histories contribute to residual susceptibility, highlighting the need for immunity-based surveillance and targeted interventions.
Abstract
Background Despite sustained high measles-containing vaccine (MCV) coverage, maintaining population immunity after measles elimination remains challenging. This study aimed to characterize measles antibody persistence, identify immunity gaps, and evaluate factors associated with seronegativity in China. Methods A multicenter cross-sectional serological survey was conducted among 2,083 participants from Jiangsu Province and Xinjiang Uygur Autonomous Region during 2024–2025. Measles-specific IgG antibodies were measured using ELISA, with seropositivity defined as IgG ≥200 mIU/mL. Restricted cubic spline models were used to assess antibody kinetics after excluding individuals without documented vaccination, those sampled within one month after vaccination, and potential primary vaccine failures. Multivariable logistic regression and propensity score matching were performed to evaluate factors associated with seronegativity. Results Overall measles IgG seropositivity was 84.59% (95% CI: 82.98–86.08%), with a GMT of 482.48 mIU/mL. Seropositivity varied significantly by region, ethnicity, age, and vaccination history. Antibody levels showed a non-linear decline with increasing time since vaccination, and each additional year since the last vaccination increased seronegativity risk (AOR = 1.11, 95% CI: 1.07–1.15). Children aged 8–17 months had the lowest seropositivity (28.13%), indicating a potential susceptibility window. Although migrants had higher seropositivity than permanent residents (93.04% vs. 83.90%), migration status was not independently associated with seronegativity after adjustment. Conclusions High MCV coverage does not necessarily ensure sustained population immunity in the post-elimination era. Waning humoral immunity, delayed vaccination, and heterogeneous vaccination histories contribute to residual susceptibility, highlighting the need for immunity-based surveillance and targeted interventions.