Ananova:

Swiss researchers have found a rare case of a patient contracting HIV twice.

The patient picked up a different strain of the virus over two years after the first infection.

Doctors once assumed that patients' natural immunity would keep them from getting the virus more than once.

Researchers say the new case highlights the importance of safe sex even between HIV-infected partners.

They also say it could have implications for the development of an Aids vaccine.

The 38-year-old man was successfully treated for more than two years and was taken off the drugs after getting an experimental vaccine intended to boost his immune system.

But a few months later in April 2001, his virus level jumped - weeks after he had unprotected sex. He was found to be infected with a different strain.

The study was funded by the Swiss government and drug maker GlaxoSmithKline.

"It just shows how little we understand what's happening with HIV-related immunity," said one of the scientists involved in the study.

Researchers say one vaccine may not protect against all strains, and are concerned that variations in HIV are greater than those in the flu virus, which requires a new vaccine every year.

Story filed: 05:29 Thursday 5th September 2002

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