Is bacterial pneumonia deadly?

It can be: Bacterial pneumonia can be deadly, particularly in the elderly and in people with poor immune systems (on chemotherapy, with hiv, or even uncontrolled diabetes, amongst others). There is a vaccine available to treat one of the most deadly types of bacterial pneumonia, strep pneumonia. Typically, it is given to those at highest risk of developing or having a bad outcome from bacterial pneumonia.

Maybe: In most cases patients recover from pneumonia, but in some cases ( damaged immune system, elderly, underlying coexisting disease, like emphysema) it can be fatal. Even at times in otherwise previously healthy patients some pneumonias can be extremely severe and deadly but this would be unusual.