ACCRA Seth Berkley was a young epidemiologist working for the U.S. State Department when he saw the graves left behind after measles swept through refugee camps in Sudan during the 1985 famine.
"You'd see little shallow graves, lined up, one after the other - babies. That's what happens when measles goes through a nutritionally deficient community. It's a horrible disease and it spreads incredibly efficiently," he says.
Now, as chief executive of the Global Alliance for Vaccines and Immunization (GAVI), Berkley's specialism is vaccinology and he is in Africa again, working to introduce routine childhood immunizations which protect most people in the rich world.
Here in Ghana, there have been no deaths from measles since 2003, and no cases of polio, another vaccine-preventable disease, since 2008. But Berkley's sights are set high.
His interim goal with GAVI is to save another 4 million lives by 2015, and his big mission is for the global health community to get vaccines against every preventable disease to every child who needs protecting.
"I wish we could have state-of-the-art hospitals in every corner of the earth...but realistically it's going to be a while before that can happen," he said in an interview.
"But we can immunize every kid on earth, and we can prevent these diseases. It's only a matter of political will, a little bit of money and some systems to do it."
GAVI, set up in 2000, uses private and government donor backing to negotiate down vaccine prices for the developing world and then bulk-buy and deliver them to countries whose populations need them most.
In its first decade, GAVI says it has already financed Immunization that has prevented more than 5.5 million premature deaths from common but life-threatening diseases.
After teetering on the brink of a funding crisis in late 2010, the group held a pledging conference in London last June and enlisted the help of billionaire philanthropist Bill Gates and the British government to squeeze other donors hard.
The result was $4.3 billion in pledges, substantially more than the $3.7 billion GAVI had asked for and enough to keep the alliance's programs in more than 70 of the world's poorest countries funded until 2016.
Berkley says GAVI's success lies in the sheer size of the market it has created, making it hard for pharmaceutical companies to ignore.
"The concept of GAVI was to create a market for the entire developing world. When we're in negotiations with companies, it's not just about the Togo market or the Ghanaian market, it's about the entire market," Berkley says. "Our birth cohort is 75 million children. That's a big market."
PRICES FORCED DOWN
Since 2000, Big Pharma has gradually seen the prices of its vaccines - many of which cost $70, $90 or even several hundred dollars in the west - forced down in the developing world under pressure from GAVI's market.
Last year a raft of drugmakers including GlaxoSmithKline, Merck, Johnson & Johnson's Crucell and Sanofi-Aventis' Sanofi Pasteur said they would cut their prices on vaccines against diseases such as measles, diarrhoea and meningitis to help GAVI sustain its supplies to the world's poorest countries.
The price GAVI pays for pentavalent vaccines, which protect against diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenza type b, was also cut by the India-based firms Serum Institute and Panacea Biotec, bringing it to well below $2.00 per dose.
Yet GAVI is often criticized, in particular by the international medical charity Medecins Sans Frontieres (MSF), which says it still pays too much for some of its vaccines - effectively handing a sizeable profit and a guaranteed market to Western pharmaceutical giants like Pfizer and its British rival GlaxoSmithKline.
Pfizer and GSK signed a 10-year deal with GAVI in March 2010 to supply their patented pneumonia vaccines at a discounted price of $7 per dose for the first 20 percent and $3.50 for the remaining 80 percent - a price MSF said was too high.
"Could the price be cheaper? Probably," Berkley says. "But between the time when we roll this out - now - and the time when there is possibly going to be more competition in the market, 500,000 children would have died of pneumococcal disease.
"So what do you do, just wait and let that happen?"
Berkley admits his determination is "almost like a religious belief", but insists it is also pragmatic.
From a childhood in New York where he talked his way into helping out at a retail chemistry supply store to get closer to the science, he later worked in a ghetto clinic in Mississippi, and moved from there to study tropical medicine in Brazil. He took his first African trip to Senegal in West Africa.
"I love science and I believe in it. I have a faith that science can solve problems and make the world a better place," he says.
Asked about fears that a focus on Immunization might take attention and funds away from other areas of health, such as building hospitals and improving access to treatment, Berkley says Immunization is simple, cheap and very cost-effective.
"You can't stop wars to build tertiary teaching hospitals, but you can say 'let's stop for a couple of days to immunize the kids'. It has been done," he says.
(Reporting by Kate Kelland; Editing by Myra MacDonald)