A Nationwide Seroprevalence Study for Measles in Individuals of Fertile Age in Romania

Background/Objectives: Romania remains endemic for measles due to suboptimal vaccine coverage rates. During the last three epidemics, the highest incidence of measles was recorded in children younger than 1 year, who should have been partially protected by maternal antibodies. A nationwide cross-sectional seroprevalence study was conducted on persons of fertile age to evaluate potential immunity gaps in the population. Methods: Between June and October 2020, 959 serum samples were col-lected from individuals aged 25-44 years (46.5% females) from all the geographic re-gions in Romania. Measles IgG antibodies were assessed using an enzyme-linked immune assay (DIA.PRO-Diagnostic Bioprobes Srl, Italy). Statistical analysis was performed in IBM SPSS Statistics 27.0, using Fisher’s exact and chi-squared tests to test for associations between seropositivity and demographic factors, with p < 0.05 con-sidered statistically significant. Results: The overall measles seroprevalence was 77%, without gender- or geographic region-related differences. Both the seropositivity rate and the measles antibodies titers increased with age, with the highest difference be-tween the oldest and the youngest age group (p=0.057), suggesting persistent im-munity after natural infection in older individuals or anamnestic responses in vac-cinated persons, caused by repeated exposures to the circulating virus. An additional confirmatory pilot study on 444 pregnant women confirmed the low level of measles seroprevalence (68.4%), with a significant upward trend in older ages (75% in those aged >40 years old vs. 65% in those aged 25-29 years, p=0.018 and mean reactivity of measles antibodies 3.05+/-1.75 in those aged > 40 years vs. 2.28+/-1.39 in those aged 25-29 years, p=0.037). Conclusions. This study signals critical immunity gaps in the population that contribute to the accumulation of susceptible individuals and recur-rent measles outbreaks. The absence of measles antibodies in women of childbearing age increases the newborn’s susceptibility to infection, with potentially severe com-plications.