The study included patients aged 18 years and older, with
hematologic or solid cancer receiving active chemotherapy
during the 2010e2011 influenza season (October
2010eFebruary 2011). We included only patients insured
through Clalit Health Services, since the hospital belongs to
this health maintenance organization (HMO) and its electronic
records capture outpatient visits of this HMO and
only a small proportion of patients treated in Davidoff’s
Center belong to other HMOs