Due to Vag8’s high abundance on OMVs, presence on the outer membrane of B. pertussis and the protective effect of this protein as a potential vaccine antigen, the overactivation of the contact system described here, together with the degradation of essential complement protein described earlier (18) may have implications for the inclusion of Vag8 in novel pertussis vaccines. The gene discussed is VTN; the disease is pertussis.