TO THE EDITOR:
Influenza is an acute febrile illness caused by infection with influenza virus A&B. Clinical manifestations are fever, myalgia, and cough. Myositis (symptomatic or laboratory confirmed) and rhabdomyolysis have also been reported. (1) Influenza vaccine is recommended for populations at increased risk for developing complications.
Myopathic syndromes are one of the major adverse effects of HMG-CoA reductase inhibitors ("statins"). Only 1 case of rhabdomyolysis after influenza vaccine in a patient using statins has been reported. (2) We attempted to determine if influenza vaccine given to patients treated with statins causes asymptomatic or symptomatic myopathy.
Our study was conducted in outpatient rural clinics of Clalit Health Services in north Israel, during October 2001. Patients were eligible if they were at least 50 years of age and had received an influenza vaccine. A 5-mL blood sample for creatine phosphokinase (CPK) and aldolase levels was obtained before and 5 to 7 days after vaccination. Clinical and demographic data as well as reactions after the vaccination were recorded. We studied 98 patients: 52 who received statins and 46 controls. Their mean age was 69.7 years (range, 50-91 years). Clinical and demographic characteristics were similar in both groups.
Local reactions (tabor, pain, mild swelling) were reported in 20 patients (20.2%): 7 in the statin group and 13 in the control group (P = NS). These reactions improved after a few days without treatment. Only 2 patients (2%) (1 in each group) had myalgia. CPK and aldolase levels were measured before and after influenza vaccination for the entire study population and were analyzed separately by sex (because of sex differences in total muscle mass and normal ranges). CPK levels increased slightly, but not significantly, alter influenza vaccination in both groups of female patients, and in male patients only in the control group. The only significant change observed was an increase in aldolase levels after influenza vaccine in female control subjects (P = .013). All CPK and aldolase values before and alter vaccination were within normal ranges.
Thus, we found no indication in this pilot stud that influenza vaccination causes clinical or laboratory evidence of myopathy in patients taking statins.
REFERENCES
(1.) Middleton PJ, Alexander RM, Szymanski MT. Severn myositis during recovery from influenza. Lancer 1970: 2:533-5.
(2.) Plotkin E, Bernheim J, Ben-Chetrit S, Mor A, Korzets Z, Influenza vaccine--a possible trigger of rhabdomyolysis induced acute renal failure due to the combined use of cerivastatin and bezafibrate Nephrol Dial Transplant 2000; 15:740-1.
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