Lack of effect of influenza and pneumococcal vaccines on anticoagulation by warfarin.

The effects on anticoagulation of a purified trivalent sub-unit influenza vaccine and a 14-valent pneumococcal vaccine were investigated in a single-blind controlled study involving 69 well-stabilised warfarin recipients. There were no clinically or statistically significant alterations of anticoagulant control in vaccine recipients as compared with controls at 2, 7 and 21 days after vaccination. On the basis of these data, concern about warfarin-vaccine interaction should not deter practitioners from immunising warfarin recipients against influenza or infection with Streptococcus pneumoniae.