title: Revaccination with Live Attenuated Vaccines Confer Additional Beneficial Nonspecific Effects on Overall Survival: A Review.
abstract: BACKGROUND
  Live vaccines against measles (MV), tuberculosis (BCG), polio (OPV) and smallpox reduce mortality more than explained by target-disease prevention. The beneficial nonspecific effects (NSEs) of MV are strongest when MV is given in presence of maternal antibodies. We therefore hypothesised that revaccination in presence of prior immunity enhances beneficial NSEs.
  
  
  METHODS
  Literature search for studies of revaccination and mortality.
  
  
  RESULTS
  In two randomised trials (RCTs), two doses versus one dose of MV reduced all-cause mortality by 63% (95% CI: 23-83%) from 9 to 18months of age. In a quasi-experimental study two doses before and after 9months compared with one dose of MV after 9months of age reduced mortality by 59% (25-81%). BCG-revaccination significantly enhanced BCG's effect against overall child mortality in two RCTs. In a natural experiment study of OPV campaigns over a 13-year-period in Guinea-Bissau, each additional dose of OPV was associated with a 13% (4-21%) reduction in mortality rate. The beneficial NSEs of smallpox vaccination for survival increased significantly with the number of smallpox vaccination scars.
  
  
  CONCLUSIONS
  Revaccination with live vaccines led to substantial reductions in overall mortality. These findings challenge current understanding of vaccines and may explain the beneficial effects of campaigns with live vaccines.
authors: Bandim Health Project, Indepth Network, Apartado 861, Bissau, Guinea-Bissau; Research Centre for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark; OPEN, Odense Patient data Explorative Network, Odense University Hospital/Institute of Clinical Research, University of Southern Denmark, Denmark.
authors: Christine S
authors: CS
authors: Benn
authors: Bandim Health Project, Indepth Network, Apartado 861, Bissau, Guinea-Bissau; Research Centre for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark.
authors: Ane B
authors: AB
authors: Fisker
authors: The London School of Hygiene and Tropical Medicine, Keppel Street, London, UK.
authors: Hilton C
authors: HC
authors: Whittle
authors: Bandim Health Project, Indepth Network, Apartado 861, Bissau, Guinea-Bissau; Research Centre for Vitamins and Vaccines (CVIVA), Bandim Health Project, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark. Electronic address: p.aaby@bandim.org.
authors: Peter
authors: P
authors: Aaby
mesh_terms: D003140:Communicable Disease Control; D003141:Communicable Diseases / Q000382:microbiology / Q000401:mortality* / Q000821:virology; D006801:Humans; D007117:Immunization, Secondary; D009026:Mortality; D014611:Vaccination; D014613:Vaccines, Attenuated / Q000276:immunology*
chemical_list: D014613:Vaccines, Attenuated
keywords: BCG; Boosting; Measles vaccine; Nonspecific effects of vaccines; Oral polio vaccine; Revaccination