Low Seroprevalence of Measles-Specific IgG in Children of Three Ethnic Groups from Mexico: Influence of Age, Sex, Malnutrition and Family Size

Background: The reemergence of measles represents a public health problem. The aim of the study was to determine the seroprevalence of IgG antibodies against measles in children of three ethnic groups in southern Mexico and the nutritional status and demographic risk factors associated. Methods: A cross-sectional study in 416 school-age children, 207 belonging to the Tlapaneco ethnic group, 101 to the Mixteco group and 108 were considered Mestizo. Sociodemographic data were collected, an anthropometric evaluation of the children was performed and a fasting blood sample was obtained from each child for the measurement of measles IgG antibodies by Enzyme-Linked Immunosorbent Assay (ELISA). Results: From the total sample, 59% of the children were seropositive for IgG antibodies against measles; in contrast, 41% lacked IgG antibodies. Measles antibody seropositivity was higher in girls (64%). 90.5% of 6-year-old children had higher antibodies seroprevalence, compared to the children between 10 and 13 years old (45.5%). In the three ethnic groups, age was negatively correlated with the index standard ratio (ISR) of measles antibody levels and the families with >= 8 members showed less seropositivity. According to the antibodies levels, most of the positive cases remained around 1 Standard Deviation (SD) of the ISR values and no underweight children had antibody levels above 2 SD. Conclusions: The Anti-Measles serological coverage is low in children of three ethnic groups from Southern Mexico and the age, sex, malnutrition and family size are associated factors. Therefore, it is important to strengthen immunization campaigns, principally in vulnerable groups.