Fig. 1.

Reproducibility of the S. typhi Vi ELISA for specific IgG using sera from a recently vaccinated individual. Mean absorbance at 405 nm for the Tris buffer control, dilution 1 on the x-axis, and sera (from a recently vaccinated individual), was used to create the standard curve in the ELISA. Eight doubling dilutions of standard sera from one in 20 to one in 2560 (dilutions 2–9) were used. The mean absorbance (405 nm) ± 1 s.d. for each dilution over 18 assays is shown.