Table 1.

Antibody levels of sera used in this study

Volunteers and vaccines	Anti-S. sonnei IgG	Anti-S. flexneri2a IgG
1
S. sonnei A	1.1	1.2
S. sonnei C	84.6	1.2
2
S. sonnei A	1.0	1.3
S. sonnei C	103.2	1.2
3
S. sonnei A	<0.5	2.3
S. sonnei C	51.2	2.4
4
S. sonnei A	0.6	2.5
S. sonnei C	96.9	2.8
5
S. sonnei A	0.5	2.2
S. sonnei C	121.8	2.6
6
S. flexneri 2a A	<0.5	1.1
S. flexneri 2a C	0.8	29.3
7
S. flexneri 2a A	<0.5	1.3
S. flexneri 2a C	<0.5	66.8
8
S. flexneri 2a A	<0.5	1.2
S. flexneri 2a C	<0.5	71.5
9
S. flexneri 2a A	<0.5	1.5
S. flexneri 2a C	<0.5	51.6
10
S. flexneri 2a A	<0.5	1.8
S. flexneri 2a C	<0.5	423.5

Volunteers 1–5 were immunized with S. sonnei vaccine, and volunteers 6–10 were immunized with S. flexneri 2a vaccine. Results are given for measurements taken before (A) and 4 weeks after (C) the second immunization with the respective O-SP-conjugate vaccine. Antibody levels to the LPS of S. sonnei and S. flexneri 2a were measured by ELISA referred to a standard serum and are expressed in ELISA units.