Medical Correspondent, BBC News
Ernest is one of over 500 children in Ghana testing the vaccine
Clinical trials of a vaccine against malaria have begun in Ghana in West Africa.
Malaria kills more children in Africa than any other disease so an effective vaccine could have huge potential.
But scientists have tried and failed in the past to create a vaccine against the parasitic infection which is spread by mosquitoes.
Our medical correspondent Fergus Walsh has been to central Ghana and witnessed one of the trials first hand.
Like any young child being immunised, Ernest let out a howl when he was given the malaria jab.
But he may well live to be grateful for receiving it.
He is one of over 500 children in Ghana under the age of two, who are on the malaria vaccine trial.
Malaria is the main threat to children in Ghana and throughout sub-Saharan Africa.
It kills more children there than any other disease. It's estimated that one child dies from malaria in Africa every thirty seconds. Children have no immunity to the disease.
Malaria has been killing people for thousands of years.
Scientists have spent decades working on a malaria vaccine. But malaria has proved a formidable enemy.
There has never been a vaccine against a disease caused by a parasite.
Dr Joe Cohen of GlaxoSmithKline heads a team in Belgium which has spent more than 20 years developing the malaria vaccine.
He said it had been a hugely difficult task. "I think the main challenge is the complexity of the parasite itself.
"Parasites have devised ways of escaping the immune system of the host which are exquisite and I think that is the major reason why we haven't been able up to now to develop any vaccine against any parasitic disease," he said.
The malaria vaccine being trialled in Ghana and five other African countries is the most advanced attempt yet at creating a jab against the disease.
Malaria kills between one and three million people worldwide each year
Most of the deaths are in sub-Saharan Africa
More than a million children in Africa die from malaria each year
The phase II trial is looking at what is the best age to give the jab to children and whether they will require two or three doses.
An earlier study of the same vaccine in Mozambique showed that it reduced cases of malaria by a third and outbreaks of severe malaria by half.
But that is less effective than doctors would like, so would it warrant mass immunisation?
Dr Jennifer Evans, who's co-ordinating the vaccine trial in Agogo, said: "Over a million children a year die from severe malaria in sub-Saharan Africa, so if we are looking at saving even half of those children that would be a significant impact."
A trip round Agogo hospital shows there is an urgent need for a malaria vaccine. Half the children admitted have malaria. If their fever is not treated promptly the infection can kill in two days.
The quest for a malaria vaccine has received massive financial support from the Microsoft billionaire Bill Gates.
Through the Bill and Melinda Gates Foundation he has given more than $250 million to the Malaria Vaccine Initiative. This not-for-profit organisation aims to accelerate the global drive for a malaria vaccine.
It has signed a partnership with GlaxoSmithKline to share the costs of the vaccine trials.
Dr. Melinda Moree, director of MVI said "We are committed to making an affordable, safe, and effective malaria vaccine available as quickly as possible to those who need it most."
For it's part GlaxoSmithKline said it shared that commitment.
Dr Joe Cohen said: "I'm 100% confident that it will be made accessible to those who need it in Africa. We haven't spent more than 20 years to see this vaccine sitting on a shelf in a warehouse."
Now it's a question of waiting. The children on the trial in Ghana will be monitored for many months to see how well they're protected.
And another much bigger trial of the vaccine is required to prove its effectiveness.
If all goes to plan, the vaccine could be licensed in 2011.
A vaccine will never be the whole answer to defeating malaria. Other strategies, including the use of insecticide-treated bed-nets and antimalarial drugs, are crucial.
If a vaccine is added to those weapons, then the war on malaria really could be won.