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 .
Peer effects in learning HIV results.
How do neighbors positively or negatively influence individuals living in rural Malawi to learn their HIV results ? Using data of location of homes and distance to neighbors , we measure the social network effects of neighbors ' learning their HIV results on individuals own learning . Using the fact that  neighbors  were r and omly offered monetary incentives of varying amounts to learn their HIV results , we find positive effects of neighbors attending clinics on others living nearby : a 10 percentage point increase of the percentage of neighbors ( approximately 2.4 individuals ) learning their HIV results increases the probability of learning HIV results by 1.1 percentage points . The strongest network effects are among closest neighbors ; we find no effect among religious social networks . We also find a negative interaction between direct cash incentives and peers : the effect of peers doubles among those who were not offered any individual financial incentive to learn their HIV results
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 .