Varies. If bacterial pneumonia with fluid= effusion are caught and treated early and with appropriate antibacterial agents, then full recovery is likely. If the effusion is large, drainage by thoracic tap="thoracentesis can be diagnostic and therapeutic. Depending on age, smoking, etc. One likely needs cut scan and maybe bronchoscope to rule out cancer of the lung causing the pneumonia.
Advanced pneumonia. When someone has pnuemonia with plueral effusion the inflammation has caused fluid to accumulate outside the lung tissue and into the thoracic cavity. This usually means an advanced stage of infection. Antibiotics are indicated if bacteria are the cause. Draining the fluid requires a tube to be placed. If the effusion is not sufficiently drained it can cause permanent scarring of the lung.