Comparison of the immunogenicity and safety of two different brands of Salmonella typhi Vi capsular polysaccharide vaccine.

BACKGROUND: The recent emergence of multi-drug-resistant Salmonella strains highlights the need for better preventive measures, including vaccination. Safe and immunologic vaccines have been developed based on purified Vi polysaccharide. OBJECTIVE: To compare the immune response elicited by two different brands of Salmonella Vi capsular polysaccharide vaccine (ViCPS). SETTING AND DESIGN: Double blind, randomized (3:1), controlled, parallel, phase III study was conducted at two centres in India to compare the safety and immunogenicity of Typbar, the investigational vaccine with an already marketed vaccine "X", in healthy subjects aged between 12 -25 years. MATERIAL AND METHODS: A sample size of 184 subjects was calculated. Subjects were randomly distributed in two groups, immunized with single dose of Typbar or Vaccine "X". Serum samples were taken before 7 days and 4 weeks after immunization for the determination of antibodies to Vi polysaccharide, by ELISA method. Safety was assessed by physical examination, laboratory parameters before and after vaccination and by monitoring adverse events. Statistics: The geometric mean antibody titre (GMT) 4 weeks after vaccination was compared from respective pre-vaccination values by Wilcoxon signed rank test. Geometric mean of antibody levels before and after immunization and the ratio between them (Mann-Whitney test), the Seroconversion rates (Z test of proportions) and the adverse events (Fisher's exact test and Chi square test), were compared between two groups. P value < 0.05 was considered statistically significant. P values and 95% confidence intervals were estimated in two-tailed fashion. RESULTS: 153 subjects (Typbar =116 and Vaccine "X" =37) were studied. 71.6% (95% CI=63.4%-79.8%) and 75.7% (95% CI=64.9% - 89.5%) were the seroconversion rates with Typbar and vaccine "X" respectively. The GMT values for Vi antibodies induced after Typbar and vaccine "X" were 10.23 Typbar and 13.46 mg/mL respectively and these values showed high significance when compared to their respective pre-immunization GMT values (P<0.0001) at 95% CI (-10.49 to -7.19 mg/mL for Typbar and -14.69 to -8.86 mg/mL for Vaccine "X"). The induction of antibody response appeared to be slightly stronger (P=0.032) with vaccine "X" when compared to that of Typbar. This is justifiable as the same group also had high pre-immunization GMT values (P=0.021). CONCLUSION: The immunogenicity and safety of the investigational vaccine Typbar was found to be similar to that of already marketed brand of Vi CPS, Vaccine "X". The availability of a single dose of vaccine that is safe and effective enhances the prospective for control of typhoid fever.

Iodine content of various salt samples sold in Mangalore--a coastal city with endemic goitre.

OBJECTIVE: Iodine deficiency disorders continue to be high despite ban on sale of non-iodised salt. In order to assess the effectiveness of salt iodisation programme, a study was undertaken to assess the iodine content of salt samples sold in Mangalore. MATERIAL AND METHODS: One hundred salt samples were randomly collected from shops in Mangalore and iodine content measured using MBI iodine testing kits. RESULTS: Only 39 samples had adequate iodine of 15 ppm or more. There was a statistically significant difference in the salt samples with adequate content in rural versus urban areas (46.6% and 27.5%, respectively, with p < 0.05). Branded samples had significantly higher iodine content than non-branded salt (p < 0.05). Salt sold at Rs.2/- per kg had significantly lower iodine content than the salt sold at Rs.3-4/- per kg (p < 0.01). CONCLUSION: Salt iodisation programme is poorly implemented in Mangalore probably due to improper iodisation, inadequate storage, hot and humid weather conditions and lack of public awareness. Public education and education of shop owners regarding their role in prevention of iodine deficiency disorders may be of value in this direction.