BEIJING - Chinese scientists have succeeded in the first phase of a clinical trial of an HIV vaccine and will launch the second stage in a few months, according to the country's leading disease control expert.

Shao Yiming, chief expert of the National Center for AIDS/STD Control and Prevention, told China Daily that the second phase of experiments on the vaccine, which has been approved by the national drug administration, "is likely to start in three or four months".

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Work on the HIV vaccine was one of the 16 major science and technology projects that made significant progress during the nation's 11th Five-Year Plan (2006-2010).

Generally, a vaccine to cure an infectious disease needs to pass three phases of clinical trials, to evaluate its effect on healthy people, to test its effectiveness on people exposed to a risk of infection, and to evaluate its impact on high-risk groups.

Although a number of countries have completed second-phase tests, none has yet reached stage three.

China started research on an HIV vaccine in 1993 by conducting clinical trials with a vaccine produced outside the country.

In 2005, Chinese scientists developed a new vaccine using the smallpox vaccine as a carrier.

Smallpox was a deadly infectious disease that had been globally eradicated by the late 1970s.

"The smallpox vaccine has a long history and wide application, so we chose it for its reliability and its higher immunogenic potential," Shao was quoted as saying by the website of the central government, www.gov.cn.

Clinical trials of the new vaccine started in 2007 and, late last year, it was proved to be able to induce an immune reaction in the cells of healthy people.

"The smallpox vaccine has been used on hundreds of millions of people. All Chinese people under 25 have been vaccinated," said Shao, pointing out that this is a unique characteristic among the "more than 100 ongoing experiments in the world".

If the vaccine proves successful, it will have a huge impact on the nation's HIV prevention policy, Shao said in an earlier interview with China Central Television.

China has around 740,000 people with HIV or AIDS. The number is estimated to reach 1.2 million by the end of 2015, Hao Yao, deputy director of the Ministry of Health's disease prevention and control bureau, said in February.

Earlier this year, the State Council called for greater efforts to control the spread of HIV and improve medical services for HIV carriers and AIDS patients, including intensified research efforts and international cooperation to develop new medicines and technologies.