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 .
Vaccine Protection of Bangladeshi Infants and Young Children Against Cholera: Implications for Vaccine Deployment and Person-to-Person Transmission
Background : Killed oral cholera vaccines are internationally licensed for older children and adults , but not for infants and young children . We investigated whether mass immunization of older children and adults can confer herd protection to children too young to be vaccinated . Methods : We analyzed the first year of surveillance of an individually r and omized , placebo-controlled trial of killed oral cholera vaccines in 89,596 older Bangladeshi children and adult women .  Vaccine herd protection of children less than 2 years of age , who were too young to participate in the trial , was evaluated by determining whether the incidence of cholera during the first year of follow-up of this age group was lower in residential clusters with higher levels of vaccine coverage than in clusters with lower levels of vaccine coverage . Results : Vaccine coverage of the targeted population ranged from 4 % to 65 % in different clusters . The incidence ( cases per 1000 ) of cholera among children less than 2 years of age ranged from 18.9 in clusters in the lowest quintile of vaccine coverage to 8.6 in clusters in the highest quintile ( P = 0.004 for the inverse association between vaccine coverage and risk of cholera ) Vaccine coverage of adult women ( relative risk of cholera = 0.95 for each percent increase in vaccine coverage ; 95 % confidence interval : 0.92–0.99 ; P < 0.01 ) , but not of older children , was independently associated with a lower risk of cholera in children less than 2 years of age . Conclusions : Vaccination of older age groups was associated with protection of children too young to be vaccinated . The pronounced herd protection of young children associated with vaccination of adult women suggests that adult women may play a prominent role in the transmission of cholera to young children in this setting
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 .