Wednesday June 25 2014
The contagious bacteria can cause intense bouts of coughing
“One in five children who see a doctor with a persistent cough may have…whooping cough, new research indicates,” The Independent reports. These findings have sparked calls for teenagers to be given a booster dose of the vaccine.
Whooping cough (pertussis) is a highly contagious infection that can lead to serious complications, especially in young babies.
In the UK, children are vaccinated against the disease at two, three and four months of age (the 5-1 vaccine), with a further “booster” vaccine (the 4-1 pre-school booster) given before they go to school.
There was evidence of recent whooping cough infection in 56 out of 279 children who took part in the study (20%) and in 39 out of 215 children who had been fully vaccinated (18%).
Despite having a few limitations, this study suggests that the whooping cough vaccine may wear off in time, leaving older children vulnerable to the infection. Whooping cough can then be passed on to young babies, for whom it is particularly dangerous.
The authors recommend that the body that determines vaccine policy – the Joint Committee on Vaccination and Immunisation – should conduct further investigations into whether a booster shot during the teenage years would be an effective use of resources.
Where did the story come from?
The study was carried out by researchers from the University of Oxford, the Respiratory and Vaccine Preventable Bacteria Reference Unit in London and Public Health England.
It was funded by the National Institute for Health Research (NIHR).
The study was published in the peer-reviewed British Medical Journal (BMJ). It was published on an open-access basis, so is free to read online.
The study was covered fairly by the Mail Online and The Independent. However, the latter’s headline describing “vaccination fears” could have been more detailed, as it could give casual readers the impression of safety fears surrounding the vaccine, which is not the case.
Both papers rightly highlight the seriousness of whooping cough, referring to the 2012 outbreak, when more than 9,000 people contracted the condition and 14 young children died.
What kind of research was this?
This was a prospective cohort study used to estimate the prevalence and severity of whooping cough in school-age children who went to their GP with a persistent cough (since the introduction of the pre-school booster vaccine in 2001).
The authors point out that whooping cough is one of the most common vaccine-preventable diseases, causing nearly 300,000 deaths worldwide. In the UK, a course of vaccines for children aged two, three and four months was introduced in 1990, and a pre-school booster was introduced in 2001. However, immunity given by vaccination is reported to last between just 4 and 12 years.
They say the evidence suggests that whooping cough infections are rising in adolescents and adults, with a national outbreak declared in the UK in 2012.
An adolescent booster vaccine has been introduced in several countries, including France, Germany and the USA – but not in the UK, thus far. The study was undertaken to inform current discussions as to whether an adolescent booster vaccine should be introduced.
What did the research involve?
Between 2010 and 2012, researchers recruited 279 children aged 5 to 15, who presented to their GPs a persistent cough lasting two to eight weeks. The children came from 22 general practices in the Thames Valley area.
Children whose cough was likely to be caused by a serious underlying medical condition, who suffered from immune deficiency or had been given a pre-school whooping cough booster vaccination less than one year previously, were excluded.
Health professionals recorded information about the children, including date of birth, sex, duration of cough and household smoking. Data on previous vaccinations were extracted from medical records.
An oral fluid sample from each child was sent to the laboratory for analysis, to detect any anti-pertussis toxin antibodies. In those with confirmed whooping cough, the severity of the cough was assessed over 24 hours, using a validated cough monitor.
Researchers calculated the overall prevalence of whooping cough, as well as the prevalence in subgroups who had or had not received the pre-school booster vaccination.
They also calculated the percentages of study participants with laboratory confirmed whooping cough during the following time periods:
- one to three years
- three to five years
- five to seven years
- and seven or more years after receiving the pre-school whooping cough booster vaccination
They looked at whether the type of pre-school booster vaccination was associated with their risk of whooping cough (the booster may contain three or five components). After this, they calculated whether the time that had elapsed since receiving the pre-school booster vaccination had any association with the risk.
What were the basic results?
There was evidence of recent whooping cough infection in 56 children (20%, 95% Confidence Interval [CI] 16% to 25%).
Those with evidence of infection included 39 (18%, 95% CI 13% to 24%) of the 215 children who had been fully vaccinated.
The risk of whooping cough was more than three times higher (40%, 95% CI 26% to 54%) in children who had received the pre-school booster vaccination seven years or more previously, than in those who had received it less than seven years previously (12%, 95% CI 7% to 17%).
The risk of whooping cough was similar between children who received the five and three component pre-school booster vaccines (risk ratio for five-component vaccine 1.14, CI 0.64 to 2.03).
Four out of six children in whom cough frequency was measured coughed more than 400 times in 24 hours.
How did the researchers interpret the results?
They conclude that whooping cough can be found in one-fifth of school-age children in the UK who present a persistent cough. This is despite more than 90% coverage (the amount of children vaccinated) with the primary vaccination and about 80% coverage with a booster. They say their findings will help inform discussions of the need for an adolescent whooping cough booster in the UK.
As the authors point out, this study had some limitations, including the possibility that some children who met the criteria may not have taken part, which may have skewed the results.
It is also possible the results may not apply to other parts of the country, although the authors point out that the GP surgeries they included covered populations with a broad socioeconomic spectrum.
Only six children with whooping cough were monitored using the 24-hour monitoring of cough severity.
However, the study is still a useful contribution to the current debate over whether a whooping cough booster vaccine is needed in adolescence. Further research is required to investigate whether such a vaccine would be cost-effective.
Coughs can be common in children and are not usually serious.
You should seek advice from your GP if your child experiences:
- intense bouts of coughing, which bring up thick phlegm
- a “whoop” sound with each sharp intake of breath after coughing (although this may not occur in infants and young children – see below)
- vomiting after coughing, especially in infants and young children
- tiredness and redness in the face from the effort of coughing
While unpleasant, whooping cough is not usually serious in older children. If your GP suspects a possible diagnosis of whooping cough they will contact their local Health Protection Unit who be able to provide further advice.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.