(Daily Star) Scientists have developed a diluted version of their original vaccine with a protective injection previously dubbed the holy grail" of AIDS research. Since the epidemic began almost four decades ago only four have been tested on patients with none proving a success. The latest injection uses a form of the common herpes virus virus cytomegalovirus (CMV) that causes cold sores. The virus was weakened so it did not cause serious disease and proceeded to wipe out simian immunodeficiency virus (SIV) the monkey version of HIV in 16 out of 27 rhesus macaques. Nine out of 12 monkeys given a second dose of SIV could also still fight it off three year later. Co-corresponding author Professor Klaus Fruh said: This research using rhesus CMV provides potentially important insights into the design of a human CMV-based HIV vaccine. We significantly attenuated CMV and still got the same type of immune responses as with the wild version of this vaccine. A less powerful vaccine will make it potentially viable for humans.