There is a theoretical potential for transmission of live attenuated influenza virus in Fluenz Tetra® to immunocompromised contacts for one to two weeks following vaccination. In the US, where there has been extensive use of the Live Attenuated Influenza Vaccine, there have been no reported instances of illness or infections from the vaccine virus among immunocompromised patients inadvertently exposed. Where close contact with very severely immunocompromised patients (e.g. bone marrow transplant patients requiring isolation) is likely or unavoidable (for example, household members), however, appropriate alternative inactivated influenza vaccines should be considered. For the majority of PID patients this means that household contact with a live vaccine is fine, but if in doubt check with your immunologist.