“Can you catch pneumonia from another person?”

Yes however it is not simple to catch and it depends on if it's viral or bacterial.

Pneumonia is infection and inflammation of the lung from mostly infectious causes. It happens when a person inhales or aspirates infectious agents or substances (while drowning or asphyxiation or inebriation) and part of all of the lung (one or both) reacts and becomes compromised from performing its function of gas exchange.
The inhaled infectious agent can come from the air as respiratory droplets from another infected person. Bacterial and Viral Pneumonias are contagious - they can be transmitted from one to another via saliva/cough/sneeze etc.
People with compromised immune system like your daughter are more prone to infections than the common population.

Pneumonia is inflammation of the lungs. It can be caused by a multitude of bacteria and viruses, some can be transmitted from person to person. Most are not causing pneumonia even if they got to the body.

Pneumonia is the result of another medical condition or infection so it is not directly contagious, but the underlying cause, bacterial or viral most likely is contagious. I would recommend using precautions to avoid and fluid contact with an infected person.

Stay safe,

Justin Idle M.D/P.h.D pending 2019