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Flu News for Senior Citizens
Flu Shots Found to Also Reduce Risk of Blood Clots
in Veins by 26 Percent
Effect more pronounced before, rather than after,
age 52, with a 48%t lower risk of VTE
Nov. 10, 2008 Flu shots well established as
protection for senior citizens from influenza are being found to have
other benefits, too. A presentation this weekend at the American Heart
Associations Scientific Sessions 2008 says these inoculations appear to
also reduce the risk of blood clots in the veins by 26 percent. And, it
works best for those under age 52, which was the average age of
participants in the study.
Our study suggests for the first time that
vaccination against influenza may reduce the risk of venous thrombotic
embolism (VTE), said Joseph Emmerich, M.D., Ph.D., lead author of the
study and professor of vascular medicine at the University Paris
Descartes and head of the INSERM Lab 765, which investigates thrombosis.
This protective effect was more pronounced before
the age of 52 years.
VTE is the formation of a blood clot in a vein. The
condition is dangerous because the blood clot can break loose and travel
through the circulatory system to the right side of the heart. From
there it can go to the lungs (a pulmonary embolism), which can be
life-threatening or even fatal.
Researchers conducted a case-control study among
1,454 age- and sex-matched patients (average age 52 years) from 11
centers in France (the FARIVE study). They compared 727 patients without
personal history of cancer within the last five years who had initial
episodes of VTE to a control group of age- and sex-matched patients free
of venous and arterial thrombotic disease.
Patients younger than 18 years old or those who
already had VTE, had a diagnosis of active cancer or a history of
malignancy less than five years previously, or had a short life
expectancy due to other causes were ineligible to participate in the
study.
Potential control subjects with cancer, liver or
kidney failure, or a history of venous and/or arterial thrombotic
disease were also ineligible.
|
 The American Heart Association recommends heart
patients get annual flu shots to protect against this infectious
disease.
Patients with cardiovascular disease are more likely to die
from influenza than patients with any other chronic condition.
However, patients with cardiovascular disease should not get the nasal-spray flu
vaccine. |
Researchers interviewed patients using a
standardized questionnaire covering age, educational level, medication
history, personal and familial history of thrombotic disease, and
acquired risk factors for VTE, including pregnancy, use of oral
contraceptives or estrogen replacement therapy, trauma or surgery less
than three months previously, prolonged immobilization, or travel
lasting more than five hours.
Patients were classified as having secondary
(provoked) VTE if they had one or more of the above acquired risk
factors. All other patients were considered to have had unprovoked
episodes of VTE.
Influenza vaccination status during the previous 12
months was also recorded. The outcomes of the cases, documented through
half-yearly telephone interviews for five years, include:
● Overall, the adjusted odds risk was 26 percent
less for developing VTE after having the flu shot.
● The flu shots protective effect was more
pronounced before rather than after age 52 years, with a 48 percent
lower likelihood of VTE in those younger than 52.
● In women under 51 years, getting the flu shot
reduced the odds of developing VTE by 50 percent, and by 59 percent for
women taking oral contraceptives.
● The protective effect of vaccination was
similar for different types of VTE (deep vein thrombosis or pulmonary
embolism).
The mechanism underlying the link between influenza
virus infection and the risk of VTE is still unclear, Emmerich said.
Infections in general increase blood viscosity,
and systemic inflammatory reactions to infectious agents can themselves
trigger a thrombotic process, he said. However, influenza vaccination
might lower the risk of thrombosis in other ways, as suggested by the
even distribution of VTE events across the 12 months of the year in both
vaccinated and unvaccinated cases in our study.
Further studies are needed to confirm this
relationship between influenza vaccination and VTE, and to explore the
underlying mechanisms. It raises the possibility that flu vaccination
could be recommended after a first VTE event, Emmerich said.
The American Heart Association recommends heart
patients get annual flu shots to protect against this infectious
disease. Patients with cardiovascular disease are more likely to die
from influenza than patients with any other chronic condition. However,
patients with cardiovascular disease should not get the nasal-spray flu
vaccine.
Background Information
Co-authors are: T. Zhu, M.D., Ph.D.; L. Carcaillon,
M.D., Ph.D.; I. Martinez, M.D., Ph.D.; J. Cambou, M.D., Ph.D.; X. Kyndt,
M.D., Ph.D.; K. Rivron-Guillot, M.D., Ph.D.; M. Vergnes, M.D., Ph.D.;
and P. Scarabin, M.D., Ph.D. Individual author disclosures are available
on the abstract.
The University Paris Descartes, INSERM, FRM,
Fondation de France and Leducq funded the study.
Editors note: For more on influenza and
cardiovascular disease, visit:
http:///www.americanheart.org.
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