Seroprevalence of anti Vi antibodies and immunogenicity of Typhim Vi vaccine in children

Abstract

This prospective study was carried out on 250 children between 6 months to 5 years of age to determine seroprevalence of anti Vi antibodies and to measure seroresponse and percent seroconversion to TyphimVi polysaccharide vaccine in children 2-5 years of age. Fifty children each were enrolled between 6 to 12 months of age (Group A), between 1- 2 years of age(Group B), between 2-3 years of age (Group C), between 3-4 years of age (Group D) and between 4-5 years of age (Group E). Anti-Vi antibody baseline titres were determined in all children. Children in Groups C to E were vaccinated with Typhim Vi vaccine. Baseline and postvaccination antibody titres were determined by ELISA. Test sera which had antibody levels >1 microg/ml were scored as seropositive. Of 250 children, 3 had base line anti-Vi antibodies >1 microg/ml. Following immunization overall seroconversion rate was 77.5% with 65.3%, 78.2% and 88% children showing seroconversion in Groups C, D and E respectively. Seroconversion was significantly more in Group E children compared to Group C (p=0.0148). There were no significant adverse reactions following vaccination. The study highlights very low prevalence of baseline anti Vi antibodies in children between 6 months and less than 5 years of age and shows high immunogenicity and safety of Typhim Vi polysaccharide vaccine in children 2-5 years of age.

Fifth Percentile Cutoff Values for Antipneumococcal Polysaccharide and Anti-Salmonella typhi Vi IgG Describe a Normal Polysaccharide Response

“…We, thereby, addressed three major limitations of previous studies describing S. typhi Vi antibody responses: limited number of healthy individuals studied (15, 16), use of an in-house hence not widely available ELISA (15), radio-immuno assay (31), or bead-based assay (32) for detection of anti- S. typhi Vi antibodies and restricted age groups [in children 2–16 years (33) or 2–5 years (34) old]. A comparison of pneumococcal polysaccharide antibody response and S. typhi Vi vaccine response was recently conducted in 16 healthy volunteers, 22 common variable immunodeficiency patients, and 27 hypogammaglobulinemic patients and showed superiority of anti- S. typhi Vi vaccine responses to discriminate between groups.…”

Genomics of immune response to typhoid and cholera vaccines

“…Primary failure, as assessed by post-vaccination antibody levels, occurs in 23-40% of recipients of typhoid vaccine [19,20]. The available typhoid vaccine is a polysaccharide (PS) vaccine, an inactivated subunit vaccine composed of long chains of sugar molecules that make up the surface capsule of Salmonella enterica serotype typhi (Salmonella typhi).…”

Genetic determinants of immune-response to a polysaccharide vaccine for typhoid

“…The extent of variation in immune response has been extensively studied for some vaccines. Primary failure, as assessed by post-vaccination antibody levels, occurs in a significant proportion of vaccinees; for example, 2-10% for measles vaccine (Poland 1998;Poland et al 1999), 5-20% for hepatitis B vaccine (Milich and Leroux-Roels 2003;Zuckerman 1996), and 23-40% for typhoid vaccine (Gupta et al 2008;Sur et al 2009). …”