Why do we not have a vaccine against HIV or TB?

The Curtin Medalist for Excellence in Medical Research for 2013, Canberra’s Centenary Year, is Nobel Laureate Emeritus Professor Rolf Zinkernagel. The Medal was presented to Professor Zinkernagel for a Lifetime of Achievement at a ceremony at JCSMR. Professor Zinkernagel then presented a Public Lecture on his work entitled 'Why do we not have a vaccine against HIV or TB?' Professor Zinkernagel was awarded the Nobel Prize in Physiology or Medicine in 1996 for his research, carried out in conjunction with Professor Peter Doherty at The John Curtin School in the 1970s. The Prize was for their discoveries concerning the specificity of the cell mediated immune defence.