Safety of intramuscular influenza vaccine in patients receiving oral anticoagulation therapy: a single blinded multi-centre randomized controlled clinical trial.
BACKGROUND
Influenza vaccines are recommended for administration by the intramuscular route. However, many physicians use the subcutaneous route for patients receiving an oral anticoagulant because this route is thought to induce fewer hemorrhagic side effects. Our aim is to assess the safety of intramuscular administration of influenza vaccine in patients on oral anticoagulation therapy.


METHODS



METHODS
Randomised, controlled, single blinded, multi-centre clinical trial.


METHODS
4 primary care practices in Barcelona, Spain.


METHODS
229 patients on oral anticoagulation therapy eligible for influenza vaccine during the 2003-2004 season.


METHODS
intramuscular administration of influenza vaccine in the experimental group (129 patients) compared to subcutaneous administration in the control group (100 patients).


METHODS
change in the circumference of the arm at the site of injection at 24 hours.


RESULTS
appearance of local reactions and pain at 24 hours and at 10 days; change in INR (International Normalized Ratio) at 24 hours and at 10 days. Analysis was by intention to treat using the 95% confidence intervals of the proportions or mean differences.


RESULTS
Baseline variables in the two groups were similar. No major side effects or major haemorrhage during the follow-up period were reported. No significant differences were observed in the primary outcome between the two groups. The appearance of local adverse reactions was more frequent in the subcutaneous administration group (37,4% vs. 17,4%, 95% confidence interval of the difference 8,2% to 31,8%).


CONCLUSIONS
This study shows that the intramuscular administration route of influenza vaccine in patients on anticoagulant therapy does not have more side effects than the subcutaneous administration route.


BACKGROUND
NCT00137579 at clinicaltrials.gov.
Casajuana
Josep
J
EAP Gòtic, Institut Català de la Salut, Passatge de la Pau 1, 08001 Barcelona, Spain. josep.casajuana@camfic.org
Iglesias
Begoña
B
Fàbregas
Mireia
M
Fina
Francesc
F
Vallès
Joan-Antoni
JA
Aragonès
Rosa
R
Benítez
Mència
M
Zabaleta
Edurne
E