Pneumonia killed more than 800,000 children last year, the equivalent of one every 39 seconds, although the disease is mostly curable and preventable, global health agencies said on Friday.
In a report on what they called the "forgotten epidemic", UNICEF, Save the Children and four other health agencies urged governments to increase investment in vaccines for disease prevention, health services and medicines.
"The fact that this easily preventable, treatable and diagnosed disease remains the biggest killer of young children in the world is shocking," said Seth Berkeley, chief executive of the Gavi Vaccine Alliance.
"Millions of children are dying because of the need for affordable vaccines, antibiotics and standard oxygen therapy," said Kevin Watkins, chief executive of Save the Children. "This is a forgotten pandemic that needs an urgent global response."
Pneumonia is the cause of 15 per cent of deaths among children under five, but it receives only three per cent of spending on infectious disease research, a small percentage compared to funds for other diseases such as malaria, the report said.