Predictors of Measles and Rubella Serostatus in Mother–Infant Pairs in Rural Nepal

BACKGROUND: Measles and rubella cause serious infections in young infants, including congenital rubella syndrome, pneumonia, and disseminated disease. Measles-rubella (MR) vaccine has been recommended as a universal childhood vaccine in developing countries. National measles immunization in Nepal began in the 1980s, with rubella added in 2013. Childhood immunization with MMR (measles-mumps-rubella) in the United States has been ongoing since 1971. We compared the sero-prevalence of measles and rubella antibody in pregnant women and infants in two populations, and evaluated factors associated with negative sero-status. METHODS: Measles and rubella immunoglobulin G (IgG) antibody (AB) levels were measured in pregnant women in a placebo-controlled influenza vaccine study in southern Nepal and pregnant women at a clinic in Seattle, WA. In both cohorts, paired maternal-cord blood samples were collected at delivery: 262 pairs from Nepal (March 2012–December 2013) and 45 pairs from Seattle (December 2014–September 2015). Sera was qualitatively tested using ELISA (Zeus, Branchburg, NJ). Comparisons of proportions with protective IgG titer were performed using t-tests and Fisher’s exact tests. RESULTS: Compared with the Seattle population, pregnant women in Nepal are younger (P < 0.0001), have more children in the household (P = 0.0001), and are more likely to have preterm (P = 0.03) and low birthweight infants (P = 0.003). 244/258 (95%) pregnant Nepalese women had protective levels of measles AB vs. 44/48 (92%) in Seattle (P = 0.42). 242/258 (94%) pregnant Nepalese women had protective levels of rubella AB vs. 44/45 (98%) in Seattle (P = 0.23). 246/256 (96%) Nepalese infants had protective levels of measles AB vs. 43/45 (96%) in Seattle (P = 0.75). 238/256 (93%) Nepalese infants had protective levels of rubella AB vs. 44/45 (98%) in Seattle (P = 0.12). In 3/262 Nepal pairs, the mother had protective levels of rubella IgG AB but cord blood rubella IgG level was not protective. CONCLUSION: High rates of measles and rubella immunity were observed in both populations. Maternal rubella immunity in Nepal is a result of natural infection while immunity in Seattle is likely to be vaccination induced. As MR vaccination progresses in Nepal, further surveillance may be required to ensure continued high levels of immunity from vaccination. DISCLOSURES: J. Englund, Gilead: Investigator, Research support. CHimerix: Investigator, Research support. Alios: Investigator, Research support. Novavax: Investigator, Research support. MedImmune: Investigator, Research support. GlaxoSmithKline: Investigator, Research support. CHimerix: Investigator, Research support. Alios: Investigator, Research support. Novavax: Investigator, Research support. MedImmune: Investigator, Research support. GlaxoSmithKline: Investigator, Research support