By Fergus Walsh
Medical correspondent, BBC News
Trials in children of a new TB vaccine are underway in South Africa.
Achanté, 2, is one of those who has been immunised
The experimental jab was developed by scientists at Oxford University, and I travelled to witness the trial first hand in Worcester, north of Cape Town.
In a large garden outside a small vaccine clinic, a group of boisterous two, three and four-year-olds is playing. Their mothers sit in the shade watching.
All these children are taking part in a vital stage of a vaccine trial.
They will be among the first children in the world to receive an experimental vaccine known as MVA85A.
There is already one TB vaccine - BCG. It is no longer routinely used in the UK, but is given at birth throughout the developing world.
The problem is that BCG is not very effective - a fact made plain when you consider that more than 1.5m people a year die still die from TB.
The aim of the new vaccine is that it should be used as a booster, in addition to BCG.
I watched as first one, then another child was injected. Karin Beukes breastfed her two-year-old daughter Achanté to comfort her, as the needle went in.
Simthembile,3, has received also the jab
She has good reason to volunteer her daughter.
"My former partner died from TB," she told me. "I had TB five years ago and was very sick -that's why I want Achanté to be protected."
The second child to be immunised was three-year-old Simthembile.
He didn't even blink as he was injected - the nurse said he deserved a lolly for being so good.
Later I went home with him and his mother.
They live in a makeshift house in Mandela - an informal settlement in Worcester.
The small houses are single storey shacks, part wood, part mud bricks and corrugated iron.
Densely crowded with several people sleeping per room, these homes make ideal conditions for the spread of the bacterial disease.
Huge potential impact
The vaccine is also being tested on adults with HIV.
TB is the leading cause of death among people with HIV in South Africa.
One of the volunteers, Nandipa, told me she knew several people with HIV who had died of TB.
The vaccine was not developed in the research labs of a large pharmaceutical company.
Rather it is the brainchild of a scientist at Oxford University.
Dr Helen McShane, who is funded by the Wellcome Trust, says an effective new vaccine would have a huge impact throughout the world.
"It would reduce mortality and morbidity from this disease - obvioulsy in the developing world where the need is greatest," she said.
"But it would also be of use in areas of Europe and indeed the UK where BCG is routinely given because the prevalence of TB is so high."
Developing any new vaccine is a lengthy process.
Infected sputum samples help scientists develop the vaccine
Human testing of the new TB vaccine started six years ago, but there are still another eight years of trials needed before it could be licensed.
Most of the trials to date have been to assess safety and scientists are confident that it does no harm.
Furthermore, they know that it induces a significant immune response - stimulating T-cells - exactly what they hope an effective vaccine would do.
But the proof of concept trial will not begin until next year.
If that is successful the vaccine will go into what's called a phase three trial involving perhaps 8,000 participants.
A licence might come in 2015 - but there is no guarantee that it will be successful.
After decades of inactivity when the world seemed to have turned its back on the disease, there are five other novel TB vaccines being developed.
None is as far advanced as MVA85A, but we'll have to wait a number of years before we know which, if any, is ultimately successful.