Isotype profile of antibodies against S. suis serotype 2 after 2 doses of vaccine in 7-week-old piglets as determined by ELISA. Piglets were vaccinated with the equivalent to 109 CFU/mL of S. suis strain P1/7 bacterin formulated either with Alhydrogel® (A), Emulsigen®-D (B), or Quil-A® (C). The 1st dose was given at 3 weeks of age and the 2nd dose at 5 weeks of age. Each vaccine formulation group of vaccinated piglets (n = 10) had a corresponding placebo group of piglets (n = 10). IgM, IgG1 and IgG2 titers for individual piglets are shown with horizontal bars representing mean ± SEM. Values significantly different are shown in the graph with the corresponding P-value.