Tai chi chih is a Westernized version of the Chinese martial art that includes a standardized set of slow movements combined with meditation and relaxation.

Psychiatry Prof. Michael Irwin of the University of California Los Angeles led the 25-week study on 112 adults aged 59 to 86.

Participants were divided into two groups, with half taking tai chi chih classes three times a week for 16 weeks, and the rest taking health education classes on stress management, diet and sleep.

After 16 weeks, both groups were given a dose of shingles vaccine.

At the end of 25 weeks, immunity levels were two times higher among the tai chi group than those in the other group, the researchers said in the April issue of the Journal of the American Geriatrics Society.

"Since older adults often show blunted protective responses to vaccines, this study suggests that tai chi is an approach that might complement and augment the efficacy of other vaccines, such as influenza," said Irwin.

The varicella zoster virus that causes chickenpox in children may lie dormant until immunity wanes later in life, resulting in shingles. The intensely painful infection affects about one-third of people over 60.

The results suggest tai chi chih boosts shingles immunity and adds to the benefit of the shingles vaccine in older adults, the researchers concluded.

The U.S. National Institute of Aging and the National Center for Complementary and Alternative Medicine funded the research.