By Jon Herskovitz

JOHANNESBURG (Reuters) - Trying to prevent HIV infection through vaginal gels or daily tablets has proven ineffective in the southern African region ravaged by the disease because people failed to use the medicines as required, a study released on Monday said.

A ground breaking study issued in 2010 indicated a vaginal gel containing a prescription drug can sharply reduce HIV infections in women who use it before and after sex, raising the possibility to slow the spread of the disease by giving women a way to protect themselves.

However, a test of the gel and two types of related pills among more than 5,000 women in South Africa, Zimbabwe and Uganda showed that, based on blood tests, more than 70 percent did not use their medication as instructed.

"We are obviously disappointed in the results. We were very hopeful that these products, which we know have been effective in other studies and clearly have a lot of promise, would work," Jeanne Marrazzo, a researcher on the project for the University of Washington, told reporters in a teleconference.

"Women did not use consistently any of the products. Adherence was very low," said Marrazzo, part of the project known as the Vaginal and Oral Interventions to Control the Epidemic (VOICE).

East and southern Africa are the areas most heavily affected by the HIV epidemic. Out of the total number of people worldwide in 2009 living with HIV, 34 percent were in 10 countries of southern Africa, according to the U.N. Programme on HIV/AIDS.

Experts have been searching for years for inexpensive, safe and simple medications to decrease the risk of transmission among a population that is largely destitute and with little access to quality health care.

The study also found the group most likely to contract HIV - unmarried women under 25 - was also the most likely not to use any of the medicines. Findings were presented to the Conference on Retroviruses and Opportunistic Infections in Atlanta

The three-year study that started in September 2009 tested a daily tablet called Truvada, which was approved in July 20102 by the U.S. Food and Drug Administration for HIV prevention and associated with a 42 percent reduction in HIV infection risk.

Other drugs tested were a product called tenofovir gel, which a study said reduced HIV infections in women by 39 percent over two and a half years. An oral tenofovir tablet was also tested.

Researchers have been trying for years to formulate a microbicide - a gel, cream, ring or tablet inserted into the vagina or rectum before sex to prevent transmission of the human immunodeficiency virus that causes AIDS.

"We need to rethink the design of these intervention trials that are being done in healthy people because it is difficult for anybody to take a pill or anything every day, particularly when you are healthy and do not feel that you need a drug," said Marrazzo.

Truvada is made by Gilead Sciences, which also developed tenofovir. In 2006, Gilead assigned a royalty-free license for tenofovir gel to CONRAD.

(Reporting by Jon Herskovitz; Editing by Michael Roddy)

Also on HuffPost: