Almost 26 years after HIV was discovered to be the cause of AIDS, a vaccine has at last shown signs of protecting people. Results of the RV144 trial on 16,000 volunteers in Thailand show that those receiving the vaccine reduced their risk of HIV infection by about a third – the first evidence that a vaccine might work. The two largest previous vaccine trials, in 2003 and 2007, failed, and that had researchers wondering if there would ever be an effective vaccine.
So is this result – announced on Thursday by the US National Institutes of Health, which funded the trial – the momentous breakthrough we've been waiting for, or are the results too modest to get excited about? New Scientist takes a look.