TY - JOUR
T1 - Effectiveness of Vi capsular polysaccharide typhoid vaccine among children
T2 - A cluster randomized trial in Karachi, Pakistan
AU - Khan, M. Imran
AU - Soofi, Sajid Bashir
AU - Ochiai, R. Leon
AU - Habib, Mohammad Atif
AU - Sahito, Shah Muhammad
AU - Nizami, S. Qamaruddin
AU - Acosta, Camilo J.
AU - Clemens, John D.
AU - Bhutta, Zulfiqar A.
N1 - Funding Information:
We thank the Bill & Melinda Gates Foundation for funding the project and GSK for donating the vaccines and for providing training and support on Good Clinical Practice training. We also thank the following persons: Jeremy Farrar, R-Bradley Sack, Eunyoung Kim, Sue Kyoung Jo, John Wain, Amanda Walsh, Jon M Albert, Anne-Laure Page and the staff that worked for the following groups: Department of Pediatrics, Aga Khan University, Pakistan; University of Oxford-Wellcome Trust Research Unit at The Centre for Tropical Diseases, Ho Chi Minh City, Vietnam; University of Western Ontario, London, Canada; WHO, Geneva, Switzerland; IVI, Seoul, Korea, and the private doctors and community leaders who assisted with the trial.
PY - 2012/8/3
Y1 - 2012/8/3
N2 - Background: Typhoid fever is endemic in Karachi, with an incidence among children ranging from 170 to 450 per 100,000 child-years. Vaccination strategies are important for prevention, and the Vi capsular polysaccharide (ViCPS) vaccine has been shown to be effective in reducing the burden of typhoid fever. Methods: A cluster randomized trial was conducted in three low socioeconomic urban squatter settlements in Karachi, Pakistan between 2002 and 2007. Subsamples were followed up for assessment of immune response and adverse events after vaccination. Results: The study participants were similar in a wide variety of socio-demographic and economic characteristics at baseline. A total of 27,231 individuals of the total target population of 51,965 in 120 clusters either received a ViCPS vaccine (13,238 [52% coverage]) or the control Hepatitis A vaccine (13,993 [53%]). Typhoid fever was diagnosed in 30 ViCPS vaccine recipients and 49 Hepatitis A vaccine recipients with an adjusted total protective effectiveness of 31% (95%CI: -28%, 63%). The adjusted total vaccine protective effectiveness was -38% (95%CI: -192%, 35%) for children aged 2-5 years and 57% (95%CI: 6%, 81%) for children 5-16 years old. Conclusion: The ViCPS vaccine did not confer statistically significant protection to children in the study areas, and there was a decline in antibody response 2 years post-vaccination. However, the ViCPS vaccine showed significant total protection in children 5-16 years of age, which is consistent with other studies of ViCPS vaccine conducted in India, Nepal, China and South Africa. These findings suggest that ViCPS vaccination of school-aged children will protect the children of urban, typhoid endemic areas against typhoid fever.
AB - Background: Typhoid fever is endemic in Karachi, with an incidence among children ranging from 170 to 450 per 100,000 child-years. Vaccination strategies are important for prevention, and the Vi capsular polysaccharide (ViCPS) vaccine has been shown to be effective in reducing the burden of typhoid fever. Methods: A cluster randomized trial was conducted in three low socioeconomic urban squatter settlements in Karachi, Pakistan between 2002 and 2007. Subsamples were followed up for assessment of immune response and adverse events after vaccination. Results: The study participants were similar in a wide variety of socio-demographic and economic characteristics at baseline. A total of 27,231 individuals of the total target population of 51,965 in 120 clusters either received a ViCPS vaccine (13,238 [52% coverage]) or the control Hepatitis A vaccine (13,993 [53%]). Typhoid fever was diagnosed in 30 ViCPS vaccine recipients and 49 Hepatitis A vaccine recipients with an adjusted total protective effectiveness of 31% (95%CI: -28%, 63%). The adjusted total vaccine protective effectiveness was -38% (95%CI: -192%, 35%) for children aged 2-5 years and 57% (95%CI: 6%, 81%) for children 5-16 years old. Conclusion: The ViCPS vaccine did not confer statistically significant protection to children in the study areas, and there was a decline in antibody response 2 years post-vaccination. However, the ViCPS vaccine showed significant total protection in children 5-16 years of age, which is consistent with other studies of ViCPS vaccine conducted in India, Nepal, China and South Africa. These findings suggest that ViCPS vaccination of school-aged children will protect the children of urban, typhoid endemic areas against typhoid fever.
KW - Developing countries
KW - Immunogenicity
KW - Pakistan
KW - Typhoid fever
KW - Typhoid vaccine
UR - http://www.scopus.com/inward/record.url?scp=84864014095&partnerID=8YFLogxK
U2 - 10.1016/j.vaccine.2012.06.015
DO - 10.1016/j.vaccine.2012.06.015
M3 - Article
C2 - 22721899
AN - SCOPUS:84864014095
SN - 0264-410X
VL - 30
SP - 5389
EP - 5395
JO - Vaccine
JF - Vaccine
IS - 36
ER -
