title: A potential bias in the estimation of vaccine efficacy through observational study designs.
authors: K S
authors: KS
authors: Joseph
authors: A
authors: A
authors: Joseph
mesh_terms: D015982:Bias; D016022:Case-Control Studies; D002675:Child, Preschool; D015331:Cohort Studies; D006801:Humans; D007223:Infant; D011055:Poliovirus Vaccine, Oral / Q000627:therapeutic use*; D012107:Research Design / Q000592:standards*
chemical_list: D011055:Poliovirus Vaccine, Oral