Biomarkers and assessment of vaccine responses

Vaccines for infectious diseases have in the past, and will into the future, relied on a variety of surrogate markers to monitor vaccine efficacy. The primary surrogate markers have been either the antibody titer to vaccine antigens or the measurement of antibody function such as anti-viral neutralizing activity. In recent years, the measurement of T-cell function in conjunction with or independent of antibody measurements have been used to assess vaccine efficacy. ELISPOT, flow cytometry and intra-cellular staining methods are used to determine the impact of vaccines on immune mediators such as interleukins, interferons, MHC expression and pro-inflammatory mediators. The relevant B-cell and T-cell surrogate markers for vaccine efficacy is dependent on the vaccine being used, so that no universal set of surrogate markers can be applied to all vaccines. The use of T-cell surrogate markers can be complicated by the lack of sensitivity to accurately measure intra-cellular mediators. Although typically this is not a problem for infectious disease vaccines, it is a major problem for cancer vaccines.