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 .
Indirect Effect of 7-Valent Pneumococcal Conjugate Vaccine on Pneumococcal Carriage in Newborns in Rural Gambia: A Randomised Controlled Trial
Background Gambian infants frequently acquire Streptococcus pneumoniae soon after birth . We investigated the indirect effect of 7-valent pneumococcal conjugate vaccine ( PCV-7 ) on pneumococcal acquisition in newborn Gambian babies . Methods Twenty-one villages were r and omised to receive PCV-7 to all subjects ( 11 vaccinated villages ) or to infants aged 2–30 months ( 10 control villages ) . Other control villagers received Meningococcal C conjugate vaccine . From 328 babies born during the trial , nasopharyngeal swabs were collected after birth , then weekly until 8 weeks of age when they received their first dose of PCV-7 .  Pneumococcal carriage and acquisition rates were compared between the study arms and with a baseline study . Results 57.4 % of 2245 swabs were positive for S. pneumoniae . Overall carriage was similar in both arms . In vaccinated villages fewer infants carried pneumococci of vaccine serotypes ( VT ) ( 16.9 % [ 31/184 ] vs. 37.5 % [ 54/144 ] , p<0.001 ) and more carried pneumococci of non-vaccine serotypes ( NVT ) ( 80.9 % [ 149/184 ] vs. 75.7 % [ 109/144 ] , p = 0.246 ) . Infants from vaccinated villages had a significantly lower acquisition rate of VT ( HR 0.39 [ 0.26–0.58 ] , p<0.001 ) and increased acquisition of NVT ( HR 1.16 [ 0.87–1.56 ] , p = 0.312 ) . VT carriage ( 51.6 % vs. 37.5 % , p = 031 in control and 46.1 % vs. 16.8 % , p<0.001 in vaccinated villages ) and acquisition rates ( HR 0.68 [ 0.50–0.92 ] , p = 0.013 in control villages and HR 0.31 [ 0.19–0.50 ] , p<.001 in vaccinated villages ) were significantly lower in both study arms than in the baseline study . NVT carriage ( 63.2 % vs. 75.7 % , p = 0.037 in control and 67.2 % vs. 75.3 % , p = 0.005 in vaccinated villages ) and acquisition rates ( HR 1.48 [ 1.06–2.06 ] , p = 0.022 ) and ( HR 1.52 [ 1.11–2.10 ] , p = 0.010 respectively ) were significantly higher . Conclusion PCV-7 significantly reduced carriage of VT pneumococci in unvaccinated infants . This indirect effect likely originated from both the child and adult vaccinated population s. Increased carriage of NVT pneumococci needs ongoing monitoring . Trial Registration IS RCT N Register
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 .