Table 1.

Clinical and immunological responses to live attenuated vaccines derived from S. flexneri 2a strain 2457T and to the wild-type parent in trials conducted at the Center for Vaccine Development

ImmunogenDose (CFU)aNo. of subjectsNo. (%) of subjects with:Anti-LPS IgA ASC
DiarrheaFeverDysenteryNo. (%) respondersbGeometric mean
CVD 1207106 700000.1
107 70006 (100)c 6.1
108 30002 (67)5.3
109 12d 1 (8)007 (64)8.7
1010 6e 1 (20)f 005 (100)e 35.2
CVD 1203 (18)106 100006 (60)13.0
108 112 (18)1 (9)1 (9)10 (91)43.0
109 113 (27)7 (64)3 (27)11 (100)175.0
Wild-type 2457T (17)g 102 73 (43)2 (29)3 (43)5 (71)18.4
103 1210 (83)10 (83)10 (83)11 (92)239.0
  • a Volunteers were assigned to a dose group, for the purpose of assessing dose response, by rounding the inoculum received in 0.5-log-unit increments to the nearest log value.

  • b Response was defined as a geometric mean postvaccination count per 106 PBMC of >2 standard deviations above the mean prevaccination count.

  • c Two subjects were excluded from the analysis of IgA anti-LPS responses. One recipient of 107 CFU had a prevaccination IgA anti-LPS ASC level of 20, and one recipient of 1010 CFU had no blood sample for measurement of IgA anti-LPS ASC on day 10.

  • d One recipient of this inoculum vomited once.

  • e One subject was excluded from analysis of clinical symptoms because she developed an acute febrile respiratory influenza A illness.

  • f This subject also experienced three episodes of vomiting.

  • g Protective efficacy against shigellosis following rechallenge was 70%; P = 0.003.