Initial analysis confirmed that an HIV vaccine from a halted trial does not prevent or quell infection, according to data presented today at the HIV Vaccine Trials Network meeting.

According to the press release from Merck, the investigational vaccine (V520) was not shown to be effective at preventing infection or reducing viral load in patients who became infected during the course of the trial. This analysis confirms the earlier findings on about half of the halted trial patients, released September 21.

Other preliminary analysis indicated that for patients with a pre-existing immunity to the vector carrying the HIV genes as a vaccine there were actually more cases of infection than with placebo.

Anthony Fauci, director of the National Institutes of Allergy and Infectious Disease, said in a statement that the data show no clear reason why the vaccine would not be effective and that these initial results were both "disappointing and puzzling."