Various disease syndromes caused by respiratory syncytial virus (RSV) may have a common mechanism of pathogenesis mediated by cytokines produced by type 2 T helper cells. The nature of the immune response to RSV is determined by the pattern of cytokines produced sequentially by many different cell types. Vaccination can influence the types of cytokine produced by selectively activating T cell subpopulations and inducing an immune response that clears the virus with minimal immunopathology.