London - Cases of a life-threatening form of pneumonia that affects the young are rising rapidly in Britain. It now affects around 1,000 children a year. The cause of the increase is unknown but experts fear a vaccine in the immunisation programme could be contributing. This severe pneumonia infects the lining of the lungs called the pleura, making it hard to breathe. It requires hospital admission to drain the chest cavity. The children affected are frightened and in pain and many undergo surgery to scrape out the contents of the pleura ~ a process called surgical debridement. Child health specialists say cases of the pneumonia, known as serotype 1, have risen tenfold in a decade. They warn that a vaccine against pneumococcal disease called Prevenar, introduced in 2006, could be fuelling the rise.

The vaccine is given at two, four and 13 months and provides protection against seven of the commonest types of pneumonia. It is safe and highly effective ~ cases of invasive pneumococcal disease caused by the serotypes covered by the vaccine have fallen by 90 per cent in two years. But there are more than 90 known strains of the bacterium that causes pneumonia. When one is eliminated, it creates an opportunity for another to take its place. In the US, where Prevenar was introduced in 2000, researchers have reported an emergence of "sero-replacement" disease ~ types of pneumonia not covered by the vaccine.

Dr David Spencer, at the Freeman Hospital, Newcastle, will present figures on the growth in pneumococcal disease to the Royal College of Paediatrics annual conference in York today. "It looks as if serotype one is becoming more virulent," he said. "We have had four cases in the past week in Newcastle with empyema (the accumulation of septic fluid in the pleural cavity). These children are seriously ill and suffer a lot of pain."