Sex-based differences in mumps immunity after a third dose of measles-mumps-rubella vaccine.

BACKGROUND

A third dose of measles-mumps-rubella (MMR3) vaccine is recommended for mumps outbreak control, but the magnitude and durability of MMR3-induced immunity and the effect of sex on those outcomes, remain incompletely characterized.

METHODS

A total of 214 healthy individuals with two prior MMR doses received MMR3. Blood samples were collected at baseline (D0), day 28 (D28), and 18 months (M18) post-vaccination. Mumps-specific IgG, IgG avidity, and neutralizing antibodies (nAb) were measured by IgG ELISA and plaque reduction microneutralization assay. Cytokine and chemokine secretions from peripheral blood mononuclear cells (PBMCs) were profiled using multiplex assay.

RESULTS

Median IgG sample index values increased from 2.12 at D0 to 2.64 at D28 (p = 0.0019), and 2.85 at M18 (p < 0.001). IgG avidity rose slightly from 79.54% at D0 to 81.88% at D28 and 86.87% at M18. nAb titers (ND50) increased from 50.48 at D0 to 67.00 at D28 (p = 0.0014), and 60.18 at M18 (p = 0.044). Despite these statistically significant changes, fold increases across time points were small (IgG: 1.15-1.13; avidity: 1.03-1.08; and nAb: 1.2-1.18). Of the 21 cytokines and chemokines analyzed, only interferon-γ induced protein 10 (IP-10/CXCL10) showed significant increase and was negatively correlated with D28/D0 changes in IgG titers (r = -0.23; p = 0.014), but not with M18 changes, avidity, or nAb responses. Biological sex significantly influenced both IgG and IP-10 responses.

CONCLUSIONS

MMR3 conferred limited additional humoral and cellular immune benefits, with notable sex-dependent effects. These findings support MMR3 use primarily in outbreak settings and identify IP-10 as a potential biomarker associated with MMR3 immunogenicity.