Present and future directions for a Vi polysaccharide vaccine in preventing Typhoid fever

Abstract

AbstrakDua pendekatan yang saling melengkapi pada saat ini dikembangkan untuk memperbaiki dan meningkatknn penggunakan vaksin Vi poLisakarida kapsul (CPS). Dilakuknn studi vaksin konjugat yang terdiri clari V digabung dengan toxoi1 tetanus murni (Vi-TT) pacta percobaan fase I pada 52 orang dewasa, umur I 9-3 3 tahun. Dua injeksi ( There was no sertous adverse event af'ter any of the injections. Anti-Vi antibody let,els, measurecl by raclio-immunoassay (RIA) before ancl I weeks after first injection, indicated that all subjects in the V-TT group were seroprotectecl (>-I 1t"g/ml) after vaccination, comparecl to 88'57o of those who received Vi alone. Seroconversion , defined by 4-fold increase over baseline of total serLtm anti-V, was achieved by 80.7Vo of V-TT vaccinees afier the first injection, increasing to 84.67o after the second injection, comparecl to 73.0Vo anct 69.2% with Vi olone. As anticipated, the second dose of V|-TT did not eticit a booster response. After the secontl dose of vaccine, signfficantly higher antibody titres were found in the V-TT group (GMT 6.8 St"g/ml) comparecl with the Typhim V@ group (GMT 3.0 1t g/ml). Typhoict Four weeks after injection, 90.9Vo of enrolled subject seroconverted for anti-V antibotly (4-fold increase), ancl B6.4Vo were consklerecl seroprotected (2 I 1t'g/ml). The anti-Vi antibody GMTvalue (RIA) increased from 0.15 p.g/mt before vaccination to 2.04 1tg/ml. Serological resub of initially HAV-negative subjects were satisfactory, with a anti-HAv Lntibody GMT (moclifiecl RIA) of 176.g 1t g/mt four weeks afrer injection, and all subjects being seroprotected (2 20 1tg/ml). In the coming years, we can look forward to important advances in the clevelopment of these new vaccines that wiII be of benefit to both children and aclults living in countries endemic for these iùfectious diseases.