2010. showed that samples from Indian women caused larger reductions in vaccine titers, corresponding to their neutralizing activity levels (19). Further, the breast milk samples from Indian women had the highest rotavirus-specific IgA titers among samples from women from India and three other countries (United States, Vietnam, and South Korea), with up to 4-fold differences in median titers. Trang et al. (53) investigated the differences in rotavirus-specific IgA titers in breast milk samples from women from rural and urban settings. They showed that women from rural areas had higher levels of rotavirus-specific IgA in breast milk than those of their urban counterparts. Nonspecific immune factors in breast milk, including glycoproteins and mucins, may also influence vaccine efficacy and effectiveness by inhibiting the replication of rotavirus (45, 46, 54, 55). Lactoferrin and lactadherin have been RCGD423 shown to reduce rotavirus vaccine strain infectivity in microneutralization assays, and similar results were also seen in plaque reduction assays (20). These results strengthened the hypothesis that nonantibody breast milk components play a role in RV efficacy and effectiveness. By investigating this hypothesis, Moon et al. showed that women from LMIC (India and South Africa) had higher lactoferrin and lactadherin levels than their Ywhaz counterparts from an HIC (United States) (20). Breast milk samples from other LMIC in Africa, Latin America, and Asia should be tested for lactoferrin and lactadherin levels before broader conclusions can be reached. OBSERVATIONAL CLINICAL STUDIES OF MATERNAL IMMUNITY AND ROTAVIRUS VACCINE RESPONSES Several observational studies have examined the association between breastfeeding and RV immunogenicity. A case-control study in Germany performed by Adlhoch and colleagues found that children who were exclusively breastfed were less likely to seroconvert (56). In Zambia, higher maternal breast milk IgA titers prior to immunization were associated with a RCGD423 lower frequency of infant seroconversion in response to the monovalent RV. In that study, there was a statistically significant decrease in the percentage of children who seroconverted from the lowest to the highest cumulative breast milk IgA quartile, with seroconversion rates of 71%, 54%, 51%, and 46% (13). Yet a study conducted in Nicaragua did not find an association between rotavirus-specific IgA titers in breast milk on the day of infant immunization and the immunogenicity of the pentavalent RV (22). Further, they did not find an association between the innate antiviral factors in breast milk, including lactoferrin, lactadherin, and tenascin-C, and RV responses (57). One observational study from Nicaragua found a significant association between high maternal rotavirus-specific IgG titers in serum and the failure to seroconvert in response to the pentavalent RV in infants (22). Similar results were seen in a South African cohort, in which higher levels of prevaccination IgG and IgA were associated with lower immunogenicity of the monovalent RV (23). CLINICAL TRIALS OF ROTAVIRUS VACCINE EFFICACY IN BREASTFED AND NONBREASTFED INFANTS AND INTERVENTIONS TO IMPROVE ROTAVIRUS VACCINE EFFICACY Two approaches were used to assess the effect of breastfeeding on infant RV efficacy in clinical trials. The first involved comparisons of RV efficacies in breastfed and bottle-fed infants (58,C62). These studies were undertaken predominantly in HIC and found no statistically significant difference in seroconversion frequency between children who were fed formula RCGD423 and those who were breastfed, although numbers of seroconverters tended to be slightly higher for formula-fed children. No such studies have been performed in LMIC, likely because of the high prevalence of breastfeeding as opposed to bottle feeding. The second area of investigation was withholding of breast milk feeding at the time of vaccination. Clinical trials of breastfeeding withholding at the time of monovalent RV administration have been performed in South Africa, RCGD423 India, and Pakistan (63,C66). In these settings, lactating women and their infants were recruited and randomly allocated to groups for withholding of breastfeeding for 1 h (South Africa and Pakistan) or 30 min (India) prior to and after vaccination, while control groups breastfed normally. Despite high compliance of the mothers, none of these studies reported differences in seroconversion rates between infants who had breast milk withheld prior to vaccination and those who did not. While the clinical trials described above seem to refute the hypothesis that breast milk immunity interferes with RV seroconversion, some additional factors should be considered. The clinical trials that reported no differences in breastfed and formula-fed infants were conducted in HIC, so further investigation of the differences in.