The findings appear to suggest that additional serotypes may need to be added to the current pneumococcal vaccine to provide protection from ear infections.
From September last year, routine pneumococcal vaccines for children under two were introduced in England and Wales to cut the rate of frequent ear infections.
Acute otitus media is the most commonly treated bacterial infection in children.
But US researchers have now identified a strain of the bacteria Streptococcus pneumoniae that is not covered by the pneumococcal 7-valent conjugate vaccine.
For this latest study, the researchers examined the shifts in bacteria causing ear infections following the introduction of the pneumococcal vaccine in the US.
Two populations of healthy children aged 6 to 36 months were included in the study.
The first group of children consisted of those who had experienced their first or second acute otitus media episode in life, while the second group consisted of children with difficult to treat otitus media.
All the children in the study had received the pneumococcal vaccine between September 2003 and June 2006.
Among 1,816 children in whom acute otitus media was diagnosed, middle ear fluid samples were taken from 212 children, yielding 59 cases of S pneumoniae infection.
The researchers found that one strain of S pneumoniae belonging to the serotype 19A was a new genotype and was resistant to all antibiotics approved in the US for use in children with ear infection.
This strain was identified in nine children, four of which had been unsuccessfully treated with two or more antibiotics.
Lead researcher Dr Michael Pichichero, from the University of Rochester in New York, said that the observations were clearly worrying, especially as there were no new antibiotics available for acute otitis media in children.
‘The study suggests that an expanded pneumococcal conjugate vaccine to include additional serotypes may be needed sooner than previously thought.’
The study is available at http://jama.ama-assn.org/.
Comment below and tell us what you think