A private U.S.-based AIDS research organization says the second phase of testing has begun in London on a vaccine designed to help prevent the spread AIDS in East Africa.

Officials with the International AIDS Vaccine Initiative say 26 volunteer test subjects were vaccinated Thursday in London. A spokeswoman for the initiative, Isabelle Claxton says the initial tests of the vaccine had shown it be to be safe for human use. In the second phase, it is now being tested for effective dosage size and frequency.

Ms. Claxton says the vaccine is being tested against a sub-type of HIV specific to Kenya and East Africa. It must pass three phases of testing before it can be made available to the general public.

Ms. Claxton says the vaccine was developed after studying a group of prostitutes in Nairobi who appeared to be resistant to the AIDS virus. She says scientists studied the women's blood and how their immune systems fought against the disease.

Ms. Claxton stresses the vaccine is not designed to cure AIDS or provide total protection against the disease. But she says if it proves effective, it would be a valuable tool in controling the spread of the AIDS.

Some information for this report provided by Reuters.