Streptococcus suis is a major cause of death and disease losses, especially among recently weaned pigs. While it may respond to antibiotics, it remains difficult to control since there are many strains that cause sickness. This study was conducted to measure the amount and variation in the antibody response of pigs vaccinated. Vaccination can be very cost effective if the vaccine is designed to control the type of bacteria causing disease. A custom-made vaccine called an autogenous bacterin can be produced from bacteria that are isolated from an untreated sick pig. In this situation the protection from disease depends on the presence of antibody in the serum of vaccinated pigs. This study was conducted in a herd experienced to disease due to S. suis. The difficulty was that the S. suis causing disease in the herd were resistant to penicillin. An autogenous bacterin was developed and pigs were vaccinated at weaning. The autogenous bacterin failed to increase antibody levels in vaccinated pigs and was not economically justified.