Influenza vaccine and anticoagulation control in patients receiving warfarin.

The effects of a trivalent split virion influenza vaccine on anticoagulation control were prospectively evaluated in a sample of well-controlled warfarin recipients. Vaccine-induced changes in prothrombin time ratios were not detected during one month of follow-up after immunisation. The results are supported by the findings of other studies conducted in this country and the USA, which have all refuted the conclusions of early reports that suggested a possible interaction between warfarin and influenza vaccine.