Potential extended haplotype associations with variations in rubella vaccine-induced cytokine secreted levels in our study population may also implicate an immunological role of the proteins encoded by the HLA (A-C-B)-LTA-TNF-LST1-HLA (DRB1-DQA1-DQB1-DPA1-DPB1) gene cluster in immune response to rubella vaccine. The gene discussed is LST1; the disease is rubella.