The objective of the present work is to prepare and evaluate the effectiveness of a locally prepared
polyvalent vaccine against mastitis from the most common causes of mastitis. Staphylococcus aureus,
Streptococcus agalactiae and Escherichia coli were the most prevalent bacteria recovered from clinical
and subclinical mastitis. Montanide ISA-206 adjuvanted inactivated polyvalent vaccine containing the
three strains was prepared. Twenty pregnant cows were inoculated intramuscularly with the prepared
polyvalent vaccine two months prior to calving and boostering at day 21 from the primary injection.
Serum samples from vaccinated and non-vaccinated cows were collected at the 1^st, 3^rd, 8^th, 12^th, 16^th, 20^th
and 24^th weeks post vaccination and evaluated immunologically using ELISA. The results showed that
immune response was significantly higher in the vaccinated group than that of controls. These results
could be indicated the safety and effectiveness of the vaccine in reduction of incidence and severity of
clinical cases of mastitis but further studies should be done to elucidate the possibility of field application
and effectively.