Hi Dore,
In most part of the world, blood screening procedures are not as vigorous as they need to be. There will always be the chance of contracting HIV through blood transfusion, i.e. an odd chance of HIV infected blood bag slipping through the cracks.
On the contrary, even if the screening process is very tight, upon contact, the HIV virus cannot be detected for 4-12 weeks. This scenario is very dangerous for thalassemia patients.
For example, God forbid a person contracts HIV today, and donate blood within 4-12 weeks, there is a 'HUGE' probability that the HIV will not be detected on blood screening. The time HIV remains undetected, the infected person can infect others.
Worldwide, every day 7,000 people contract HIV. 2 million people died last year with AIDS alone.
The vaccine is a huge step, for patients receiving regular blood transfusions.