Serum Bactericidal Assay is used as a measure of vaccine-induced antibody function in conjunction with complement to destroy bacteria.This can give information on whether a particular serum sample has a level  of bactericidal antibodies enough to reach a protective threshold. SBA assays can also provide percentage seropositivity (%SP) of subjects surpassing the protective threshold. Serum reactivity against various bacterial isolates can be evaluated using the traditional viable count technique.