Pneumonia is the single biggest killer of children in the world. Although deaths are rare here in New Zealand, our children have rates of pneumonia hospitalisation five times greater than the United States and other developed countries, predominantly among disadvantaged children.

Why are we so concerned about early childhood pneumonia? Young infants and children are more susceptible to pneumonia than adults. Pneumonia is a chest infection - the term chest infection just sounds less threatening.

It can start as a "cold" with runny nose, sore throat and mild cough but then develops into either a wheezing illness with breathing difficulties (bronchiolitis) or breathing difficulties with cough and fever but no wheeze (pneumonia). In infants this is usually caused by virus infection of the lungs, although bacterial infection can follow.

Pneumonia can have serious consequences, including further infections, further admissions over the next years, or the development of irreversible lung scarring (bronchiectasis). New Zealand children are 18 times more likely to develop bronchiectasis than children in Britain, with even higher risks in Maori and Pacific children.

The type and frequency of the lung scarring seen here is only found in other severely disadvantaged communities such as Australian Aboriginal, Native American and Native Alaskan communities.

As well as the social, emotional and economic implications for families, there are economic implications for health services.

It has been calculated that childhood pneumonia has direct medical costs of over $7 million per year for New Zealand. The indirect costs are even higher.

So why do New Zealand children have this appalling health statistic with such a long health shadow? There is good evidence that our houses are not child-friendly and are cold, damp and overcrowded.

Our immunisation rates remain low making children more susceptible.

We cannot immunise against every organism, but pneumonia and/or irreversible scarring has been shown with whooping cough (pertussis), influenza, measles, HiB (haemophilus influenzae), TB and pneumococcus which we can immunise against.

Immunisation also reduces the risk of death during influenza epidemics.

Smoking during pregnancy has a permanent effect on children's lungs and a smoking environment in the house and car continues the damage and/or creates new inflammation of the lungs.

Breast-feeding provides protection as well as nutrition, and there is good evidence that malnutrition is linked to the frequency of chest infections. Babies who are three months or younger at the start of winter are more susceptible to respiratory illnesses and therefore require more protection.