Table 4 shows the associations of TfR (as an indicator of iron-deficient erythropoiesis) and vaccine response. Controlling for sex, birthweight, anthropometrics, inflammation, vitamin A status and maternal antibodies, TfR at age 24 wk was the strongest risk factor for seronegativity against diphtheria at 18 mo (p = 0.0334). The gene discussed is TFRC; the disease is diphtheria.