We identified three primary mechanisms of spillovers : reduced disease transmission , social proximity and substitution of re sources within households .
We found the strongest evidence for spillovers through reduced disease transmission , particularly vaccines and mass drug administration .
In general , the proportion of a population receiving an intervention was associated with improved health .
We found evidence of publication bias for certain spillover estimates but not for total or direct effects .
Conclusions We found the strongest evidence for spillovers from vaccines and mass drug administration to control infectious disease .
There was little high quality evidence of spillovers for other interventions
Background Many interventions delivered to improve health may benefit not only direct recipients but also people in close physical or social proximity .
Our objective was to review all published literature about the spillover effects of interventions on health outcomes in low-middle income countries and to identify methods used in estimating these effects .
Effectiveness of Vi capsular polysaccharide typhoid vaccine among children: a cluster randomized trial in Karachi, Pakistan.
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 r and omized trial was conducted in three low socioeconomic urban squatter settlements in Karachi , Pakistan between 2002 and 2007 . Sub sample s 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
We identified three primary mechanisms of spillovers : reduced disease transmission , social proximity and substitution of re sources within households .
We found the strongest evidence for spillovers through reduced disease transmission , particularly vaccines and mass drug administration .
In general , the proportion of a population receiving an intervention was associated with improved health .
We found evidence of publication bias for certain spillover estimates but not for total or direct effects .
Conclusions We found the strongest evidence for spillovers from vaccines and mass drug administration to control infectious disease .
There was little high quality evidence of spillovers for other interventions
Background Many interventions delivered to improve health may benefit not only direct recipients but also people in close physical or social proximity .
Our objective was to review all published literature about the spillover effects of interventions on health outcomes in low-middle income countries and to identify methods used in estimating these effects .