Study: Untreated depression decreased effectiveness of shingles vaccine

Shingles, a reactivation of the chickenpox virus that causes painful blisters and rashes, often occurs in individuals older than 60. There's a vaccine for it, but a new study published in Clinical Infectious Diseases suggests a link between untreated depression in older adults and decreased effectiveness of the herpes zoster shot.

A two-year study led by Michael Irwin at the University of California-Los Angeles showed that depressed patients not being treated with antidepressants had lower immunity to the varicella-zoster virus and did not respond to the shingles vaccine as well as those who were not depressed. Researchers tested 40 individuals aged 60 or older with a major depressive disorder and compared the results with a control group of 52 individuals in the same age range.

Patients with untreated depression were "poorly protected by shingles vaccination," Irwin said. Meanwhile, treatment for depression helped bump up the cell-mediated immunity and increased the effectiveness of the drug, helping to "normalize the immune response to the zoster vaccine," he said.

Though larger studies are needed, the research published is a step toward understanding how antidepressants potentially increase the efficacy of vaccines. If antidepressants help boost the efficacy of the shingles vaccine in those with depression, can such treatment affect the immune response of depressed patients to other vaccines?

Only 16% of individuals age 60 and older received the jab for shingles, according to U.S. health authorities. Merck's ($MRK) Zostavax is the approved shingles vaccine in the U.S.

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