Fig. 1

Description of the analyzed studies and causal diagrams. AD: autoimmune disease, IRR: incidence rate ratio, DAG: Directed Acyclic Graph, CI: confidence interval, CMI, cell-mediated immunity, Ctrl: control, DM1/DM2: type 1/type 2 diabetes mellitus, COPD: chronic obstructive pulmonary disease, GE: gastroenteritis, HPV: human papillomavirus, HR: hazard ratio, HZ: herpes zoster, RV: rotavirus, VE: vaccine effectiveness, VZV: varicella zoster virus. Study 1 [8]. DAG: The causal association between DM2 and the risk of HZ was controlled for other factors that might be associated with risk, such as age and underlying cardiac disease and COPD. The square around S = 1 indicates that the analysis is conditional on having been selected into the study. Individuals with renal disease, hepatic disease, metabolic syndrome, history of HZ, or with immunocompromising conditions were excluded from enrolment. The exposure and other factors are associated with the outcome (HZ) via two mediators; waning CMI and VZV reactivation. Study 2 [9]. DAG: S = 1 refers to the selection criteria applied during the study. The square around S = 1 indicates that the analysis is conditional on having been selected into the matched cohorts, age and practice region being the matching factors. The analysis was adjusted for the potential confounders “use of health care resources” and “other vaccinations”. Study 3 [10]. DAG: The square around S = 1 indicates that the analysis is conditional on having been selected into the case-control study. Controls were matched to cases for age and hospital and subjects with previous nosocomial GE or contraindications to RV vaccination were excluded. The analysis was controlled for potential confounders (maternal education, household size, sex, etc.)