In the future, however, lifelong immunosuppression may not be required, she said.

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"In particular the need for and risks of long-term immunosuppression, and the fact that functioning of the transplant may be both delayed and limited, " it said.

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"There is some immunosuppression that occurs during pregnancy, " she said.

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Currently, cancer patients are not candidates for face transplants because transplant recipients must take immunosuppression drugs for life so that the body does not reject the donated tissue, Siemionow said.

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The woman is undergoing a strict regimen of immunosuppression therapy so her body does not reject the donor skin, a problem that has been encountered in other skin transplants, the doctors said.

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About two-thirds of the patients in the series had at least one underlying medical condition that would put them at higher risk for influenza and its complications, Schuchat said, citing chronic lung disease, immunosuppression, heart disease, obesity and pregnancy as examples.

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