Effect of Influenza Vaccination of Healthcare Personnel on Morbidity and Mortality Among Patients: Systematic Review and Grading of Evidence

(See the Editorial Commentary by Griffin on pages 58–60.) Background. Influenza vaccination of healthcare personnel (HCP) is recommended in>40 countries. However, there is controversy surrounding the evidence that HCP vaccination reduces morbidity and mortality among pa-tients. Key factors for developing evidence-based recommendations include quality of evidence, balance of benefits and harms, and values and preferences. Methods. We conducted a systematic review of randomized trials, cohort studies, and case-control studies published through June 2012 to evaluate the effect of HCP influenza vaccination on mortality, hospitalization, and influenza cases in patients of healthcare facilities. We pooled trial results using meta-analysis and assessed evidence quality using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. Results. We identified 4 cluster randomized trials and 4 observational studies conducted in long-term care or hospital settings. Pooled risk ratios across trials for all-cause mortality and influenza-like illness were 0.71 (95 % con-fidence interval [CI],.59–.85) and 0.58 (95 % CI,.46–.73), respectively; pooled estimates for all-cause hospitalization and laboratory-confirmed influenza were not statistically significant. The cohort and case-control studies indicated significant protective associations for influenza-like illness and laboratory-confirmed influenza. No studies reported harms to patients. Using GRADE, the quality of the evidence for the effect of HCP vaccination on mortality and in