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 .
Herd immunity in adults against influenza-related illnesses with use of the trivalent-live attenuated influenza vaccine (CAIV-T) in children.
Highest attack rates for influenza occur in children . Immunization of schoolchildren with inactivated influenza vaccine in Michigan and Japan was associated with decreased morbidity and mortality , respectively , in older community contacts . An open-labeled , non-r and omized , community-based trial in children with the cold adapted influenza vaccine , trivalent ( CAIV-T )  was initiated to determine the coverage necessary to reduce spread of influenza in the community . Age-specific baseline rates of medically attended acute respiratory illness ( MAARI ) for Scott and White Health Plan ( SWHP ) members at intervention ( Temple and Belton ) and comparison communities ( Waco , Bryan , and College Station ) were obtained in 1997 - 1998 . During three subsequent vaccination years , 4298 , 5251 and 5150 children received one dose per season of CAIV-T.  Vaccinees represented 20 - 25 % of the age-eligible children .  Age-specific MAARI rates were compared for SWHP members in the intervention and comparison sites during the influenza outbreaks . Baseline age-specific MAARI rates per 100 persons for the influenza season were comparable between the intervention and comparison communities . In the subsequent three influenza seasons , the age groups 35 - 44 , 45 - 54 , 55 - 65 and > 64 years experienced reductions in MAARI rates in the intervention communities . In adults > or = 35 years of age , significant reductions in MAARI of 0.08 ( 95 % CI : 0.04 , 0.13 ) , 0.18 ( 95 % CI : 0.14 , 0.22 ) and 0.15 ( 95 % CI : 0.12 , 0.19 ) , were observed in the influenza seasons for vaccination years 1 , 2 and 3 , respectively . No consistent reduction in MAARI rates was detected in the younger age groups . Vaccination of approximately 20 - 25 % of children , 1.5 - 18 years of age in the intervention communities result ed in an indirect protection of 8 - 18 % against MAARI in adults > or = 35 years of age
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 .