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In acute-care hospitals, no evidence of a protective effect of healthcare worker (HCW) vaccination on hospital-acquired influenza (HAI) in patients has been documented. Thomas Benet, of Hospices Civils de Lyon in Lyon, France, and colleagues, sought to ascertain the effectiveness of influenza vaccination of HCWs on HAIs among patients.
A nested case-control investigation was implemented in a prospective surveillance study of influenza-like illness (ILI) in a tertiary acute-care university hospital. Cases were patients with virologically-confirmed influenza occurring >=72 h after admission, and controls were patients with ILI presenting during hospitalisation with negative influenza results after nasal swab testing. Four controls per case, matched per influenza season (2004-05, 2005-06 and 2006-07), were randomly selected. Univariate and multivariate conditional logistic regression models were fitted to assess factors associated with HAI among patients.
In total, among 55 patients analyzed, 11 (20 percent) had laboratory-confirmed HAI. The median HCW vaccination rate in the units was 36 percent. The median proportion of vaccinated HCW in these units was 11.5 percentÂ for cases vs. 36.1 percentÂ for the controls (P = 0.11);Â two (20 percent) cases and 21 (48 percent) controls were vaccinated against influenza in the current season (P = 0.16). The proportion of >=35 percentÂ vaccinated HCW in short-stay units appeared to protect against HAI among patients (odds ratio = 0.07; 95 percentÂ confidence interval 0.005-0.98), independently of patient age, influenza season and potential influenza source in the units.
The researchers say their observational study indicates a shielding effect of more than 35 percentÂ of vaccinated HCW on HAI among patients in acute-care units. They add that investigations, such as controlled clinical trials, are needed to validate the benefits of HCW vaccination on HAI incidence in patients. Their research was published in BMC Infectious Diseases.
Reference: Benet T, et al. Influenza vaccination of healthcare workers in acute-care hospitals: a case-control study of its effect on hospital-acquired influenza among patients. BMC Infectious Diseases 2012, 12:30 doi:10.1186/1471-2334-12-30