Efficacy of a locally produced, Chinese Vi polysaccharide typhoid fever vaccine during six years of follow-up.
A locally produced Vi polysaccharide vaccine against typhoid fever was licensed in China following two placebo-controlled, efficacy trials conducted in the early 1990s in Baoying, Jiangsu Province, and Quan-zhou, Guangxi Province. The two trials each enrolled over 80,000 participants and followed participants for 12 and 19 months post-vaccination, respectively. To define the long-term efficacy of this vaccine, we retrospectively assessed the occurrence of typhoid fever, diagnosed with clinical and serological criteria, in the two study populations for 6 years following vaccination. During the second year following vaccination, vaccine efficacy was 100% (95% CI: 17%, 100%) in Baoying and 85% (95% CI: 49%, 96%) in Quan-zhou. There was suggestive protection (51%; PE: -95%, 88%) during the third year in Baoying, nearly identical to the level observed in the third year of an earlier trial in South Africa. These results confirm that this vaccine protects for at least 2 years, and are consistent with the assertion that the vaccine protects for at least 3 years.
Acosta
Camilo J
CJ
International Vaccine Institute, SNU Research Park, San 4-8 Bong-Cheon 7 Dong Kwanak-Ku, Seoul 151-818, South Korea.
Hong-Hui
Yang
Y
Ning
Wang
W
Qion
Gao
G
Qun
Deng
D
Xiaolei
Ma
M
Baode
Zhou
Z
Liu
Wei
W
Danovaro-Holliday
M Carolina
MC
Ochiai
R Leon
RL
Wang
Xuan-Yi
XY
Kim
Deok-Ryun
DR
Zhi-Yi
Xu
X
Bai-Qing
Dong
D
Galindo
Claudia M
CM
Clemens
John D
JD
D000942:Antigens, Bacterial / Q000276:immunology*; D002681:China; D005500:Follow-Up Studies; D006801:Humans; D011135:Polysaccharides, Bacterial / Q000276:immunology* / Q000627:therapeutic use*; D012189:Retrospective Studies; D016896:Treatment Outcome; D014435:Typhoid Fever / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D014436:Typhoid-Paratyphoid Vaccines / Q000008:administration & dosage* / Q000276:immunology / Q000627:therapeutic use
D000942:Antigens, Bacterial; D011135:Polysaccharides, Bacterial; D014436:Typhoid-Paratyphoid Vaccines; C057664:Vi polysaccharide vaccine, typhoid