Kandulna, Ambrose KumarUttam, Kheya GhoshSharma, ShrikantKumar, M RaviPrasad, K SivaramGoyal, Vimal KantJangid, Sanjay KumarDaultani, PavankumarMittal, RavindraMaithal, Kapil2023-08-252023-08-252022-05Kandulna Ambrose Kumar, Uttam Kheya Ghosh, Sharma Shrikant, Kumar M Ravi, Prasad K Sivaram, Goyal Vimal Kant, Jangid Sanjay Kumar, Daultani Pavankumar, Mittal Ravindra, Maithal Kapil. Long-term Persistence of Immunogenicity After Primary Vaccination and Response to Booster Vaccination With Typhoid Conjugate Vaccine: Results of a Phase IV Extension Study. Indian Pediatrics. 2022 May; 59(5): 388-3920079-60610974-7559http://imsear.searo.who.int/handle/123456789/225332Objective: To evaluate the persistence of antibodies three years after primary vaccination with typhoid conjugate vaccine (TCV) of either Cadila Healthcare Ltd. (Cadila-TCV) or Bharat Biotech International Ltd. (Bharat-TCV) administered in a previous phase II/III study, and to study the booster dose response to Cadila-TCV. Methods: This was an open-label, phase IV extension study conducted in tertiary care and multispecialty hospitals in India. 112 subjects (Cadila-TCV-57, Bharat-TCV-55) who had participated in previous study were enrolled. Of these, eligible subjects received a single-dose of Cadila-TCV and were followed-up for 28 days post-booster. Primary outcome was persistence of antibodies 3 years after primary vaccination and seroconversion (?4-fold rise in antibody titre from baseline) 28 days postbooster. Safety was based on reported adverse events (AEs) post-booster. Results: The baseline GMT reported in the current study was significantly higher than pre-vaccination GMT reported in the previous study. 89/112 (79.5%) subjects had antibody titer ?10 IU/mL at baseline; eligible subjects (n=17) who had baseline antibody titre <10 IU/mL were administered booster dose. All the vaccinated subjects showed seroconversion post-booster. The GMTs reported at 10 days and 28 days post-booster were significantly higher as compared to GMTs reported after primary vaccination in previous study. 4 (23.5%) vaccinated subjects reported 9 AEs; all were solicited and of mild/moderate intensity. Conclusion: There was a significant persistence of immunogenicity after primary vaccination with both the TCVs, and robust immune response after booster vaccination with Cadila-TCV.EfficacyProtectionSafetyLong-term Persistence of Immunogenicity After Primary Vaccination and Response to Booster Vaccination With Typhoid Conjugate Vaccine: Results of a Phase IV Extension StudyJournal ArticleIndiaDepartment of Medicine, GCS Medical College, Hospital and Research Centre, Ahmedabad, GujaratDepartment of Pediatrics, Institute of Child Health, Kolkata, West BengalDepartment of Medicine, SMS Medical College and Hospital, Jaipur, RajasthanDepartment of Medicine, Indo-US Superspeciality Hospital, Ameerpet, Hyderabad, TelanganaDepartment of Pediatrics, Gandhi Medical College and Hospital, Secunderabad, TelanganaDepartment of Pediatrics, Panchsheel Hospital, Yamuna Vihar, DelhiDepartment of Medicine, Hi-Tech Medical College and Hospital, Bhubaneswar, OdishaCadila Healthcare Ltd., Ahmedabad, Gujarat.