In rural Bangladesh, family contacts of patients with cholera were studied prospectively to examine whether protection against colonization and disease due to Vibrio cholerae O1 was associated with circulating antibodies to V. cholerae. Family contacts (1,071) of 370 patients with cholera were visited daily for 10 days, cultured for V. cholerae, and queried about diarrhea. Sera collected on days 1 and 21 were assayed for vibriocidal antibodies, IgG and IgA antibodies to cholera toxin, and IgG antibodies to lipopolysaccharide (LPS). Vibriocidal titers of ⩾20 present in 50% of contacts by 20 years of age were associated with protection against both colonization and disease. An elevated Level of IgG antitoxin was not associated with protection against colonization or disease but was the most sensitive indicator of recent symptomatic cholera and of immune response to the oral immunogen B subunit. IgG antibody to LPS and IgA antitoxin were of little value in predicting colonization or disease.

Author notes

Use of trade names and commercial sources is for identification only and does not imply endorsement by the U.S. Public Health Service or the Department of Health and Human Services.
This work was supported by funds from the International Centre for Diarrhoeal Disease Research, Bangladesh (lCDDR,B), Swedish Agency for Research Cooperation with Developing Countries (SAREC), and the Swedish Medical Research Council.
We thank the field workers of the Special Studies Branch and K. M. B. Hossain and M. Ali of the Microbiology Branch of the Matlab Field Station; C. Olbing and O. Engstrom of the University of Göteborg; Drs. B. J. Stoll, M. Yunus, A. Baqui, W. B. Greenough, and D. Sack and J. Gomez and M. Siddiqui of the ICDDR,B; Drs. J. Feeley, R. Feldman, P. Blake, and S. Martin of the Centers for Disease Control; Dr. M. H. Merson of the World Health Organization; and Dr. A. Z. Kapikian of the National Institute of Allergy and Infectious Diseases for help in conducting, analyzing, and reviewing this study.
Please address requests for reprints to Dr. Roger I. Glass at his present address: Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Building 7, Room 103, Bethesda, Maryland 20205.
During the performance of this work Dr. Glass was on assignment from the Enteric Diseases Branch, Division of Bacterial Diseases, Center for Infectious Diseases, Centers for Disease Control, Atlanta, Georgia.