Background: We conducted the first trial to assess the safety and immunogenicity of an oral, killed enterotoxigenic Escherichia coli plus cholera toxin B-subunit vaccine in children <2 years old.
Methods: Three doses of vaccine or killed E. coli K-12 control were given at 2-week intervals to 64 Egyptian infants, 6 to 18 months old, in a randomized, double blind manner. Adverse events were monitored for 3 days after each dose. Blood was collected before immunization and 7 to 10 days after each dose to assess vaccine-specific serologic responses.
Results: There was no statistically significant intergroup difference in the percentage of subjects reporting the primary safety endpoint (diarrhea or vomiting) after the first (31%, vaccine; 30%, control) or third (14%, vaccine; 18%, control) dose, whereas there was a trend toward greater reporting in the vaccine group after Dose 2 (36%, vaccine; 18%, control; P = 0.052). The percentage of children showing IgA seroconversion after any dose was higher in the vaccine than the control group for recombinant cholera toxin B-subunit (97% vs. 46%), colonization factor antigen I (61% vs. 18%) and coli surface antigen 4 (39% vs. 4%) (P < 0.001 for each comparison). IgG seroconversion rates in the vaccine and control groups were 97 and 21% to recombinant cholera toxin B-subunit (P < 0.001), 64 and 29% for colonization factor antigen I (P < 0.01), 53 and 21% for coli surface antigen 2 (P < 0.05) and 58 and 4% for coli surface antigen 4 (P < 0.001), respectively. The third vaccine dose was followed by augmented IgG antitoxin titers.
Conclusion: The oral enterotoxigenic E. coli vaccine was safe and immunogenic in this setting in Egyptian infants.