When young children have pneumonia, giving them an antibiotic may be no more helpful than giving them none.

Antibiotics are only effective for bacterial pneumonia, not viral, and it is often difficult to tell the difference. So doctors often prescribe an antibiotic for children just in case. But young children with pneumonia, who have a lower probability for bacterial infection, may not need them.

Researchers studied 294 children with pneumonia, aged 3 months to 18 years, whose pneumonia was diagnosed by chest X-ray or clinical impression and who had been treated as outpatients. Half were given prescriptions for antibiotics, and half were discharged from the emergency room without a prescription. The groups were matched for many characteristics, including age, sex, severity of illness. The study is in Pediatrics.

Of the 294 children, 8.8 percent failed treatment — that is, they had to return to the hospital for admission or have a change in antibiotics. But there was no statistical difference in treatment failure between the children who got antibiotics at discharge and those who did not.