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LARGE-SCALE FIELD TRIAL OF TY21A LIVE ORAL TYPHOID VACCINE IN ENTERIC-COATED CAPSULE FORMULATION

Three doses, given within one week, of Ty21a attenuated Salmonella typhi oral vaccine in an enteric-coated formulation provided 67% efficacy for at least 3 years in a randomised, placebo-controlled field trial involving 109,000 schoolchildren in Santiago, Chile. Increasing the interval between doses to twenty-one days did not enhance protection. Significantly less protection followed administration of vaccine in gelatin capsules with sodium bicarbonate. Ty21a provides the same level of protection as the heat/phenol-inactivated whole cell parenteral vaccine but differs in not causing adverse reactions. Ty21a may now be regarded as a practical public health tool.

Lactobacillus prophylaxis for diarrhea due to enterotoxigenic Escherichia coli.

In vitro and animal experiments indicated that lactobacilli might prevent Escherichia coli from colonizing the intestine and may produce substances counteracting enterotoxin. Lactinex, a commercial preparation of dried Lactobacillus acidophilus and L. bulgaricus, is marketed for uncomplicated diarrhea. Preliminary experiments in nonfasting volunteers indicated that lactobacilli in this preparation colonized the small intestine for up to 6 h. To evaluate the protective efficacy of Lactinex, a double-blind randomized study was carried out in which 48 volunteers (23 receiving Lactinex and 25 receiving placebos) were challenged with E. coli strains that produced heat-stable or heat-labile enterotoxins or both. No significant differences between the two groups were noted with respect to attack rate, incubation period, duration of diarrhea, volume and number of liquid stools, and coproculture yields. These data suggest that this lactobacillus preparations does not prevent or alter the course of enterotoxigenic E. coli diarrhea in adults. Lack of efficacy occurred despite efforts to maximize small bowel colonization, including administration of Lactinex in milk and in a 6-hour-interval regimen during 36 h before and 96 h after challenge.

ORAL THERAPY WITH GLUCOSE ELECTROLYTE SOLUTION

Doctors Kahn and Blum based their views on oral rehydration on only 7 cases, and they fail to provide their methodological details. In their letter on oral rehydration with UNICEF/WHO (United Nations International Childrens Emergency Fund/World Health Organization) glucose electrolyte solution (GES), they maintain that hyperkalemia is a danger of GES therapy, that hypernatremia will be aggravated, that therapy should not last for longer than 24 hours, that after 24 hours monitoring of plasma potassium will be needed, and that except for developing countries where material milk is used, no plan of treatment has been proposed after the first 24 hours of rehydration. The experience of Kahn and Blum is at variance with extensive data from many carefully monitored balanced studies in infants treated with GES. GES is a potent medication and needs to be used properly. Guidelines for use are listed. Kahn and Blum fail to indicate whether their 7 patients comprised their entire treatment group or only those with biochemical or clinical problems. They also fail to indicate the degree of dehydration of the infants at onset of therapy or the extent of ongoing diarrheal losses, and they do not describe the precise treatment regimen. Their mean time of treatment -- 41 hours -- was particularly long. The hyperkalemia reported by Kahn and Blum may have resulted from excessive GES administration, without a source of free water, to infants having few diarrheal stools. Proper use of GES formula rapidly rehydrates 95-98% of mildly to severely dehydrated infants, irrespective of etiology.