LONDON (Reuters) - International donors led by Britain and Bill Gates pledged $4.3 billion on Monday to buy vaccines to protect children in poor countries against potential killers such as diarrheal diseases and pneumonia.
The funding should allow more than 250 million of the world's poorest children to be vaccinated by 2015, helping to prevent more than four million premature deaths, the Global Alliance for Vaccines and Immunisation (GAVI) said.
"Today is an important moment in our collective commitment to protecting children in developing countries from disease," said Liberian President Ellen Johnson Sirleaf, who attended the pledging conference in London.
"But every 20 seconds, a child still dies of a vaccine-preventable disease. There's more work to be done."
British Prime Minister David Cameron, who has defended increased spending on aid at a time of sharp domestic spending cuts, pledged $1.3 billion -- almost a third of the total raised, which was more than the $3.7 billion GAVI had hoped for.
Billionaire philanthropist and Microsoft co-founder Gates, a major GAVI backer who helped set up the alliance a decade ago, pledged an extra $1 billion dollars for GAVI over the next five years and praised donor governments and their taxpayers for recognizing what he calls the "magic" of vaccines.
"This is absolutely human generosity at its finest," he told reporters at a news conference. "For the first time in history, children in developing countries will receive the same vaccines against diarrhea and pneumonia as children in rich countries."
GAVI says it has helped prevent more than 5 million child deaths in the last decade with its immunization programs.
The alliance funds bulk-buys of childhood vaccines against diseases such as pneumococcal pneumonia, Hemophilus influenza type b, or Hib disease, diphtheria, pertussis or whooping cough, tetanus, measles and rotavirus.
The World Health Organization says vaccination is one of the most cost-effective public health measures. It estimates that 2 to 3 million deaths are averted each year with immunization.
A series of studies published last week found that if 90 percent of children in the more than 70 poor countries supported by GAVI were fully immunized, about 6.4 million children's lives and more than $151 billion in treatment costs and lost productivity could be saved over 10 years, producing economic benefits of $231 billion.
GAVI has been criticized by the international medical charity Medecins Sans Frontieres for paying too high a price for some of its vaccines, in particular for pneumococcal shots which it buys from the global pharmaceuticals giant Pfizer and its British rival GlaxoSmithKline.
Pfizer and GSK signed a 10-year deal with GAVI last March to supply 60 million doses a year of their Synflorix and Prevnar 13 pneumococcal shots at a discounted price of $7 per dose for the first 20 percent and $3.50 for the remaining 80 percent.
Gates defended GAVI's purchasing system and said he was always careful not to pay more than he had to. "I'm not going to spend any money that isn't directly going to help these poor children," he said. "I feel great about the prices we've got."
Several leading drugmakers including GSK, Merck, Johnson & Johnson's Crucell and Sanofi-Aventis' Sanofi Pasteur last week offered to cut some of their vaccine prices for developing countries to try to sustain supplies via GAVI.
Additional reporting by Keith Weir; Editing by Janet Lawrence