A population-based measles serosurvey in Mexico: Implications for re-emergence

Measles is a highly contagious, potentially life-threatening viral disease targeted for global elimination. Deficiencies in vaccination programs and vaccine-induced immunity waning may favor re-emergence. In 2020, Mexico experienced an outbreak, mainly affecting adults in urban areas.

To estimate vaccination-induced serostatus, we used a probabilistic population-based sample of individuals from the ENSANUT survey in 2022. Seroprevalence was estimated by plaque reduction neutralization test (PRNT) and anti-measles IgG ELISA.

Seroprevalence was 82.4 % (95 %CI 79.6, 85.0 %) by PRNT and 61.1 % (95 %CI 58.6, 63.7 %) by ELISA. The 20-29 years of age group showed the lowest PRNT seroprevalence (63.6 %), followed by the 30-39 group (71.8 %) and 40-49 (77.7 %).

Low seroprevalence in young adults suggests possible low coverage of the second dose and/or waning immunity in absence of viral circulation in the 1989-2008 birth cohorts. In case of imported introduction of measles cases, susceptibility in young adults and adults could facilitate an outbreak.