Lessons and implications from a mass immunization campaign in squatter settlements of Karachi, Pakistan: an experience from a cluster-randomized double-blinded vaccine trial [NCT00125047].
OBJECTIVE
To determine the safety and logistic feasibility of a mass immunization strategy outside the local immunization program in the pediatric population of urban squatter settlements in Karachi, Pakistan.


METHODS
A cluster-randomized double blind preventive trial was launched in August 2003 in 60 geographic clusters covering 21,059 children ages 2 to 16 years. After consent was obtained from parents or guardians, eligible children were immunized parenterally at vaccination posts in each cluster with Vi polysaccharide or hepatitis A vaccine. Safety, logistics, and standards were monitored and documented.


RESULTS
The vaccine coverage of the population was 74% and was higher in those under age 10 years. No life-threatening serious adverse events were reported. Adverse events occurred in less than 1% of all vaccine recipients and the main reactions reported were fever and local pain. The proportion of adverse events in Vi polysaccharide and hepatitis A recipients will not be known until the end of the trial when the code is broken. Throughout the vaccination campaign safe injection practices were maintained and the cold chain was not interrupted. Mass vaccination in slums had good acceptance. Because populations in such areas are highly mobile, settlement conditions could affect coverage. Systemic reactions were uncommon and local reactions were mild and transient. Close community involvement was pivotal for information dissemination and immunization coverage.


CONCLUSIONS
This vaccine strategy described together with other information that will soon be available in the area (cost/effectiveness, vaccine delivery costs, etc) will make typhoid fever control become a reality in the near future.
Khan
Mohammad Imran
MI
Department of Pediatrics, Aga Khan University, Karachi, Pakistan. mohammad.imran@aku.edu
Ochiai
Rion Leon
RL
Hamza
Hasan Bin
HB
Sahito
Shah Muhammad
SM
Habib
Muhammad Atif
MA
Soofi
Sajid Bashir
SB
Bhutto
Naveed Sarwar
NS
Rasool
Shahid
S
Puri
Mahesh K
MK
Ali
Mohammad
M
Wasan
Shafi Mohammad
SM
Khan
Mohammad Jawed
MJ
Abu-Elyazeed
Remon
R
Ivanoff
Bernard
B
Galindo
Claudia M
CM
Pang
Tikki
T
Donner
Allan
A
von Seidlein
Lorenz
L
Acosta
Camilo J
CJ
Clemens
John D
JD
Nizami
Shaikh Qamaruddin
SQ
Bhutta
Zulfiqar A
ZA