Researchers say a strain of bacteria causing pneumonia and meningitis in children is on the rise in England and Wales.
A vaccine introduced in 2006 has effectively cut the number of infections in children.
But researchers say cases caused by a pneumococcal type not covered by the vaccine seem to be increasing.
The U.S. has noted similar patterns and new vaccines are in development.
The pneumococcal vaccine protects against seven types of Streptococcus pneumoniae and is given to infants at two and four months with a booster dose at 13 months of age.
Pneumococcal infection became one of the most common causes of invasive bacterial infection in children after introduction of Hib and meningitis C vaccines. The infection can cause death.
There has been a huge fall in the number of children suffering serious illness as a result of pneumococcal infection since immunization began, according to figures from the Health Protection Agency.
Last year, government officials predicted 300 children had avoided invasive pneumococcal disease, which includes pneumonia, septicaemia and meningitis.
However, surveillance data presented at the Royal College of Paediatrics and Child Health annual scientific conference also shows serotype 1 pneumococcal may be coming in to “fill the gap”.
Dr David Spencer, consultant respiratory paediatrician in Newcastle, has been monitoring cases of empyema in children. Empyema is a complication of pneumonia involving the cavity around the lungs.
Spencer found that in most cases the disease is caused by serotype 1 and he predicts there are probably about 1,000 cases a year in the UK now compared with a handful in the early 1990s.
He says Serotype 1 is continuing to increase mostly because it’s not covered by the vaccine.
“Overall there have been very dramatic benefits from vaccination but we’re dealing with constantly shifting sands and surveillance will help us plan for the future,” said Spencer.
Currently, two vaccines are being developed which protect against serotype 1 as well as others that may be available within a couple of years.
One HPA spokesperson said they expect to see some non-vaccine strains of pneumococcal becoming more common.
There are currently 90 known pneumococcal types and vaccination protects against the seven most common types which circulate in the UK.
They say Serotype 1 was increasing prior to introduction of a pneumococcal conjugate vaccine and it is too early to tell if this trend has been exacerbated by the introduction of the vaccine.
“The increase in serotype 1 may be a coincidence and not related to the introduction of the vaccine,” said Professor Adam Finn, head of the Bristol Children’s Vaccine Centre.
He says in the U.S. they’re definitely seeing higher rates of invasive disease caused by non-vaccine types.
“You can pretty much guarantee that once one of the new broader vaccines become available we will switch to it,” he said.
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