1. Bivalent oral killed cholera vaccine: each dose of this vaccine contains V. cholerae O1 Inaba El Tor strain Phil 6973 formalin killed 600 ELISA units (EU) of Lipopolysaccharide (LPS) V. cholerae O1 Ogawa classical strain Cairo 50 heat killed 300 EU of LPS V. cholerae O1 Ogawa classical strain Cairo 50 formalin killed 300 EU of LPS V. cholerae O1 Inaba classical strain Cairo 48 heat killed 300 EU of LPS V. cholerae O139 strain 4260B formalin killed 600 EU of LPS