However, researchers at the University College London did find antibiotics were effective in substantially cutting the risk of pneumonia after chest infection -- particularly in the elderly.

Using the United Kingdom General Practice Research Database, the researchers found serious complications were rare after upper respiratory tract infections, sore throat and ear infection. Antibiotics reduced the risk, but more than 4,000 courses were needed to prevent one complication.

In contrast, the risk of pneumonia after chest infection was high, particularly in elderly people, and was substantially reduced by antibiotic use.

The study, published in the British Medical Journal, concludes that general practitioners should not base their prescribing of antibiotics for sore throat, ear infection or upper respiratory tract infections on a fear of serious complications. However, antibiotic prescribing to reduce the risk of pneumonia after chest infection is justifiable, particularly in elderly patients, the researchers said.