Ask the Experts: Effectiveness of influenza vaccine in obese patients

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Although variables make the measurement of effectiveness difficult to interpret, morbid obesity is a high-risk indication for which influenza is particularly needed.

Question. Can you speak to the effectiveness of the influenza vaccine in the obese patient?

Answer. Morbid obesity (BMI ≥40 kg/m2) is considered a high-risk indication for which influenza is especially needed. Obese patients are more susceptible to influenza disease, which may be because they are less able to mount an immune response (author's supposition). Two recent reviews in appeared in Medscape. One was a review of the Infectious Disease Society of America (IDSA) annual meeting describing a poster (abstract 538) titled Obese Individuals Respond Just as Well to Flu Vaccine. This was a serologic study showing that serum antibody levels and seroconversion were the same in obese individuals as those in nonobese patients. The other report described a study in which serological testing did not show a difference initially; however, the antibodies decreased more at 12 months in obese patients compared with nonobese patients.

We know that there are many variables, including age, type of circulating virus, previous exposure to a similar virus or vaccine, and how illness is measured, that make the measurement of effectiveness very difficult to interpret. Also, serological testing is not always a great correlate of protection.

Stephan L. Foster, PharmD, FAPhA
Professor and Vice Chair
College of Pharmacy
University of Tennessee Health Sciences Center
APhA Liaison Representative to the Advisory Committee on Immunization Practices (ACIP)
CAPT (Ret) U.S. Public Health Service


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