However, earlier studies have demonstrated that the immune response to protein (i.e., PhII) and LPS (i.e., PhI) antigens is different in cattle after a natural infection versus vaccination: natural infection preferentially induces an IgG1-response both to proteins and LPS, whereas vaccination induces an early IgG2 response to the protein p27 of C. burnetii, as well as a late and weak IgG2 response to LPS [40,41,42]. Here, GPI is linked to infection.