into  yeast ), the  virus-like particle  (VLP) vaccine against  human papillomavirus  (HPV) that is composed of the viral major  capsid  protein, and the  hemagglutinin  and  neuraminidase  subunits of the  influenza virus. Subunit vaccine is being used for plague immunization. [ edit ] Conjugate Conjugate  – certain bacteria have  polysaccharide  outer coats