THE whooping cough virus could be evolving to outwit the vaccine, according to a new study.
Scientists have warned that parts of the whooping cough, or pertussis virus, which are recognised by the vaccine, are changing, which could mean it is less effective.
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The development may have “serious consequences” in future outbreaks, according to UK researchers, writing in the Journal Of Infectious Diseases.
However, experts insisted that pregnant women should continue to be vaccinated to protect their baby when it is very young.
The vaccination campaign for expectant mothers was launched in 2012 after a large outbreak of whooping cough in the UK.
The vaccine has had a higher take-up in Scotland than south of the Border, with 78 per cent of pregnant women opting to be vaccinated.
Figures released earlier this year showed that cases of the disease had dropped dramatically north of the Border. The number of cases in children under one fell from 140 in 2012 to 19 in 2013.
However, numbers of cases of the illness UK-wide have experienced a resurgence in recent years.
During 2012, 1,926 laboratory-confirmed cases of whooping cough in Scotland were reported to Health Protection Scotland, a 16-fold increase compared with the 119 reports in 2011. Incidence remained high in 2013 with 1,188 confirmed cases.
In England and Wales in 2012, there were almost 10,000 confirmed cases – a dramatic increase from the last “peak” of 900 cases in 2008.
“We wanted to look at strains from the UK to see if there was anything sudden that had occurred that had led to these really large outbreaks,” said study leader Dr Andrew Preston from the University of Bath.
“Pertussis has a cyclical nature and the other big question is: are we going to see another increase in late 2015?”
Scientists said that a new acellular vaccine, introduced this year, could be less effective in the long term than the older vaccine, leaving teenagers and adults lacking protection.
In the latest study, researchers analysed the gene-coding for the proteins on the surface of the pertussis bacterium responsible for the UK outbreak.
They found proteins being targeted by the vaccine were mutating at a faster rate than other surface proteins not included in the vaccine. This could mean that the bacteria is changing to get around the immune system’s defences created by the vaccine.
The pertussis virus mostly affects infants, who are at highest risk of complications and even death from the illness, which often goes largely unnoticed in adults.
Dr Preston said scientists could consider options such as adding more or different proteins to the vaccine, adding chemicals which boost the immune response, or revisiting the older whole cell vaccine.
Professor Adam Finn, a paediatric immunology expert at the University of Bristol said the importance of the subtle changes found in the study was as yet unclear.
“But the control of pertussis is a significant worry,” he added. “There is very good new evidence that vaccinating pregnant women protects their babies. And the group we really want to protect is newborn babies.”
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