Seroprevalence of Measles and Rubella IgG Antibodies in Children and Pregnant Women in Iran

Background: Complete immunization against Rubella and Measles (MR) in pediatrics is achieved using 2 doses of the Measles, Mumps, and Rubella-containing vaccine (MMR) in Iran at 12 and 18 months of age, where more than 95% of children under 5 years of age are vaccinated. Antibody waning in mothers and older children, and genetic diversity in immune responses may render them susceptible to infections. Objectives: This study aimed to investigate the diversity in immunoglobulin G (IgG) antibody levels against these two viruses in pregnant women, infants younger than 2 months, children at 6, 12, and 18 months, and 5 - 6 years of age in Iran. Methods: This study was conducted on serum specimens sent to the National Reference Laboratory for Measles and Rubella in Tehran, Iran, from children under 2 months (n: 50), 6 (n: 54), 12 (n: 54), and 18 (n: 39) months, and 5 - 6 years old (n: 49), as well as women at 37 weeks of pregnancy (n: 53), from May to December 2020. Rubella and Measles-specific IgG were measured using an enzyme-linked immunosorbent assay kit. Results: Among serum samples from different provinces of Iran, the lowest positive level of Measles IgG was observed in children aged 6 and 12 months (7.41%), while the highest positive level was found in children aged 18 months (84.62%). For Rubella, the lowest IgG-positive level was seen in children aged 11 - 13 months (11.11%), while the highest positive level was observed in the 5 - 6 years old group (83.67%). Antibody levels against measles and rubella were higher in pregnant women than in children. Conclusions: Measles and Rubella antibody titers were lower in children 12 months before vaccination and reached a positive level in children aged 18 months post-vaccination. Whereas, lower Measles IgG levels in 5 - 6 years old children compared to 18 months old children may be due to waning antibodies. Pregnant women exhibited high levels of protection against these viruses (more than 80% had positive rubella IgG), as anticipated from outcomes of the national vaccination program in 2004.