Her immunosuppressive medications were stopped, and she was treated with specific immunoglobulin treatments and recovered without lasting ill effects.

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Transplant patients, who often have to take immunosuppressive drugs for long periods following surgery, could also potentially benefit from digitizing their medicine.

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Experts say vulnerable groups include pregnant women, children under five, the over-65s and those with serious conditions such as heart disease, asthma, diabetes or immunosuppressive illnesses.

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The problems arose with the dosage of current immunosuppressive drugs which would be needed for a patient to accept an organ from another person and which could ultimately prove fatal.

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There is a 0.1% risk of contracting PML if you use Tysabri in combination with other immunosuppressive drugs, but so far, no cases of PML have turned up in patients who took Tysabri alone.

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An increased risk of developing cancer may not be a major worry to most people who are having a vital organ transplanted (and is, in any case, a risk associated with existing immunosuppressive drugs), but it certainly bears some investigation.

ECONOMIST: Transplant surgery