Characterizing measles IgG-related seroprevalence in the US veteran population during the 2025 West Texas outbreak.

BACKGROUND

The 2025 United States (US) measles outbreak supports concerns that measles may have significant resurgences. The study's objectives were to characterize measles serologic testing rates, estimate measles IgG seronegativity rates, and determine independent variables associated with seronegativity across the US Veterans Health Administration (VHA).

METHODS

A nationwide retrospective, observational study was conducted, collecting data from veterans with measles IgG antibody testing performed from January through June in 2024 (preoutbreak) and 2025 (outbreak). Endpoints included determining independent variables associated with 1) measles IgG testing within the outbreak period vs the preoutbreak period, and 2) measles IgG seronegativity within the outbreak period.

RESULTS

In total, 16,446 veterans had measles IgG testing in the outbreak period, a 60.3% increase in the testing rate compared with the nonoutbreak period. Seronegativity was found in 1,220 (11.9%) veterans in the nonoutbreak period and 1,509 veterans (9.18%) in the outbreak period (P < .0001). Independent variables associated with seronegativity included age 64 years or below (OR 5.65, 95% CI 4.59-6.94), Janus kinase inhibitor use (OR 3.54, CI 1.24-10.1), and immunodeficient condition (OR 3.10, CI 2.34-4.11).

CONCLUSIONS

As measles re-emerges, certain populations were identified that may be at higher risk of infection and transmission, particularly those with immune compromise.