Safety and Immunogenicity of Salmonella Typhi Vi conjugate vaccine (Peda TyphTM) in children upto five years

Background: Conjugate typhoid vaccine can prevent increasing cases of typhoid in younger children. Commercially available conjugate vaccine has limited studies to support its use. Aims: To study the safety and immunogenicity of Vi conjugate typhoid vaccine (PedaTyph TM ). Materials and Methods: Four hundred children with age <5 years were randomised to receive either one dose (Group A) or two doses (Group B) of vaccine. Adverse effects were monitored and paired blood samples were collected for immunogenicity. Due to inadequate funding analyses of group B could not be done. Results: Adverse events occurred in 17% and 21% of children after first and second doses respectively. These events were not severe and recovered within 48 hours. Single dose of vaccine increased mean antibody titers by nine fold and seroconversion was seen in 83% of children. An 11-fold rise in mean antibody titers and seroconversion rate of 89% were noted in children below two years while six fold rise in titers and 73% seroconversion rate were recorded in children above two years. Conclusions: Vi conjugate typhoid vaccine is safe and immunogenic. Immunogenicity is better in children below two years. Single dose is not enough for seroconversion in all individuals.