4 research outputs found
Evaluation of a standardised Vi poly-l-lysine ELISA for serology of Vi capsular polysaccharide antibodies
Typhoid vaccines based on protein-conjugated capsular Vi polysaccharide (TCVs) prevent typhoid in infants and young children. Analysis of the serum anti-Vi IgG response following immunisation against typhoid confirms the immunogenicity of TCVs and forms an important part of the pathway to licensing. Comparative studies could expedite the licencing process, and the availability of a standardised ELISA method alongside the 1st International Standard (IS) 16/138 for anti-typhoid capsular Vi polysaccharide IgG (human) will facilitate this process. To this end, a non-commercial ELISA based on a coat of Vi and poly-l-lysine (Vi-PLL ELISA) was evaluated by 10 laboratories. Eight serum samples, including IS 16/138, were tested in the standardised Vi-PLL ELISA (n = 10), a commercial Vi ELISA (n = 3) and a biotinylated Vi ELISA (n = 1). Valid estimates of potencies relative to IS 16/138 were obtained for all samples in the Vi-PLL ELISA and the commercial ELISA, with good repeatability and reproducibility evident from the study results and concordant estimates obtained by the two ELISA methods. The study demonstrates that the Vi-PLL ELISA can be used in clinical trial studies to determine the immunogenicity of TCVs
Safety, immunogenicity and non-interference of concomitant Typhoid Vi capsular polysaccharide-tetanus toxoid conjugate vaccine (Typbar-TCVÂź) and measles or measles-mumps-rubella vaccines in 8â9 months-old Indian children
We evaluated safety, reactogenicity, and immunogenicity when the WHO-prequalified single-dose Typhoid Vi-polysaccharide conjugate vaccine, Typbar-TCVÂź, was administered concomitantly with measles (MV) or measles-mumps-rubella (MMR) vaccines in 8- or 9-month-old children. We enrolled 493 children who were randomized 2:1:1:1 to four groups to receive either TCV (0.5âmL intramuscularly) and MV (0.5âml subcutaneously) concomitantly at 9âmonths of age (Group 1) with two subgroups given TCV booster 28âdays (Group 1A) or 180âdays (Group 1B) later, or MV on Day 0 and TCV on Day 28 (Group 2); or TCV at 8âmonths of age and MV 28âdays later (Group 3), or MV only at 9âmonths of age (Group 4). All children received MMR at 15âmonths of age. We observed no statistically significant differences between group rates of solicited or unsolicited adverse events assessed throughout the study. Seroconversion rates for measles, mumps, and rubella antibodies were unaffected by concomitant administration with TCV, being similar in Groups 1, 2, and 3 and comparable to Group 4 (Control). IgG anti-Vi antibody titers were similar in all groups after primary Typbar-TCVÂź vaccination and were not increased by a second dose 28âdays later. A small response to a booster dose of Typbar-TCVÂź given at 180âdays did not achieve the high titers observed after the first dose, suggesting that booster vaccination may be more effective after a longer interval than 6âmonths. Typbar-TCVÂź can be safely co-administered with measles and MMR vaccines in children aged â„9âmonths. Clinical trial registration number: CTRI/2014/04/004532