To study the kinetics of humoral as well as cellular immunity to measles and to test for associated immunosuppression 124 12 month old children were studied twice, before routine MMR and either 14, 22, 30, or 38 days after vaccination. Plaque reduction neutralization (PRN) titres were determined at these time points and lymphocytes were evaluated to identify changes in proportions of phenotype, their capacity to generate cytokines and to respond to blast transformation (BT) to measles hemagglutinin (HA), tetanus toxoid and Candida antigen. The PRN titre and BT to HA plateaued at 30 days and CD8+ and NK cells increased after immunization. Interleukin 2, 4, and 10 showed no significant changes. There was mild suppression of BT at 14 and 22 days post-immunization Interferon-gamma was the principal cytokine produced after primary measles immunization, suggesting primary measles immunization induces predominantly a TH1 type response.