Two million children die each year from diarrhoea and pneumonia, making them the leading causes of death among under five-year-old children in the developing world.
World Vision estimates it would cost $3 billion to save 95% of the children who currently die from these illnesses because of lack of treatment.
The Christian development agency supports practical interventions to prevent the contraction of diarrhoea and pneumonia in the first place.
These simple measures include exclusive breast-feeding and good nutrition for babies, hand washing, safe drinking water, improved cooking stoves.
On the treatment side, there are zinc and oral rehydration solutions to cure diarrhoea, amoxicillin to cure pneumonia, and vitamin A and vaccination.
Access to basic antibiotics to treat the most common diarrhoea-causing bacteria as well as the prompt administration of oral rehydration salts can save thousands of lives, World Vision says.
In addition to making these widely available, their implentation needs to be "correct, consistent and sustained".
The development agency is focusing on treatment as well as prevention, such as ensuring clean drinking water and latrines.
It wants to see equitable access to preventions and treatments, particularly those most vulnerable and the poorest.
World Vision's child health policy expert Andrew Griffiths says: "A condition which is easily treatable in the UK can often push these children over the edge, if life-saving interventions are not available."
"Many vulnerable young children who don't have access to clean water and sanitation also suffer from other problems like malnutrition.
"Their immune systems are weakened, making them particularly susceptible to diarrhoea and pneumonia."
The comments were in response to a new series by the Lancet medical journal focusing on childhood diarrhoea and pneumonia.