Protective activity of cholera vaccines against E1 Tor cholera vibrios

With the advent of epidemic El Tor cholera there has been concern about the value of cholera vaccine prepared from classical cholera strains.Using a recently developed mouse protection test, the authors have determined the protective activity of five commercial vaccines against strains of epidemic El Tor and classical cholera vibrios. Both Ogawa and Inaba types of each kind of vibrio were used. With each vaccine, protection against El Tor vibrios was as good as that against classical cholera vibrios. There was, however, a greater than tenfold difference in the potency of the vaccines.The findings support the use of cholera vaccine for immunization against El Tor cholera and show that there are wide variations in the mouse-measured potency of lots of vaccine. The significance of the findings must await results of controlled field trials.