During the 2014/15 influenza season, a clinical study of a quadrivalent split influenza vaccination was conducted. Sixty-four volunteers ranging in age from 6 months to 18 years were recruited to study the link between cellular and humoral immune responses. Subjects were split into two groups based on neutralizing antibodies: non-primed naive/primed and seroconverted/non-seroconverted. Whole-blood cultures were stimulated with the H1N1 split antigen before and one month after the first and second vaccines for participants 13 years old, as well as before and one month after the first dosing for those 13 years old. 

One month following the initial dose, the naïve group had significant levels of IL-2, IL-12, IL-13, MCP-1, MIP-1, and TNF-. In addition to these cytokines, the production of IL-1, IL-4, IL-6, IL-8, IL-10, IL-17, G-CSF, and IFN- was raised one month after the second dosage. Except for IL-10 production, there was no significant increase in the primed group. The production of IL-2, IL-4, IL-8, IL-10, G-CSF, MCP-1, TNF-, and IFN- increased one month after the initial dose in seroconverted participants, which was faster than in the naïve group; however, there was no significant cytokine response in patients who had not been seroconverted. Those aged 13 years were primed, and subjects with seroconversion produced more G-CSF, IL-4, and IL-1. The H3N2 split antigen was also used to stimulate whole-blood cultures, generating similar cytokine profiles. Many cytokines and chemokines, including inflammatory cytokines, have been found to be produced in seroconverted people but not in non-seroconverted people.