Tablets, insertable rings and dissolving films can effectively deliver drugs to help protect women and perhaps men from infection with the AIDS virus, researchers reported on Monday.

They also found evidence that using such an approach - called a microbicide - may help overcome some of the risks of drug resistance that can come with taking pills to prevent infection.

The AIDS virus infects more than 33 million people globally and it has killed 25 million, according to the United Nations AIDS agency UNAIDS. Globally, more than half of those with HIV are women, most infected by husbands or steady partners and many of whom who are unable to insist on use of a condom.

AIDS experts have long been searching for a microbicide - a cream, gel or vaginal ring that women or men could use as a chemical shield to protect themselves from sexual transmission of the deadly and incurable virus.

On that front, here is a quick look at some of the findings coming out of the International Microbicides Conference being held in Pittsburgh:

*A flexible ring designed for use in the vagina can continually deliver two AIDS drugs, dapivirine and maraviroc, for up to a month. It has not been tested in people yet.

*A vaginal tablet worked in similar fashion, time-releasing maraviroc and another experimental HIV drug called DS003. The tablet uses a polymer designed to attach to the moist lining inside the vagina.

*A third approach uses a film - smaller and thinner than a stick of gum, similar to a mouthwash strip - to deliver the HIV drug IQP-0528.

Susan Schader of McGill University in Montreal, Canada, and colleagues said tests of these and other HIV drugs used as microbicides showed that drug resistance emerged only if HIV was in the lab dish first - which suggests people would only develop drug-resistant infections by using microbicides when they were already infected.

Microbicides using HIV drugs would represent a large new market for the companies that make the drugs, which are now used only to treat infection.

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PITTSBURGH, PA (Reuters)