Despite effective measles vaccines, measles still causes severe morbidity and mortality worldwide, particularly in developing countries. The Th2 pathway involving interleukin (IL)-4 and IL-13 cytokines, and their receptor IL-4R alpha, play important roles in the Th1/Th2 balance and antibody production. A Th2 skewing of the cytokine milieu may affect vaccine responses. We investigated IL-4, IL-13, and IL-4Ra polymorphisms and their impact on measles IgG responses and measles vaccine failure, in two separate cohorts: 12-month-old Australian children immunized with measles-mumps-rubella vaccine (n = 137) and a case/control cohort of children aged 6 months-14 years from Mozambique, Africa (n = 89), some of whom were vaccinated, but still contracted measles (vaccine failure). We found that IL-4R alpha haplotypes for Val75Ile, Ser503Pro, and Arg576Gln were associated with measles IgG in Mozambican children (p = 0.016 and p = 0.032 for Val. Pro. Arg and Val. Ser. Arg, respectively), but not Australian children. IL-4R alpha 503Pro was more prevalent in Mozambique vaccine failure cases compared with controls (p = 0.008). We showed that the impact of Th2 genes on measles vaccine responses differs between ethnicities and IL-4R alpha polymorphisms may work in combination to affect measles antibody responses and vaccine failure in Mozambican children. Studies in this area are particularly important in developing countries like Mozambique where measles is still a major health issue.