Whooping cough strikes adults as well as children. Photo: Shutterstock

An adult whooping cough booster vaccine should be “strongly considered”, according to a study showing a significant rise of the infection among older people in 2011.

That year, 26 cases of “pertussis” were recorded in Malta’s disease register compared to 30 between 2001 and 2010, according to the research published in the Malta Medical Journal.

“This means a greater than eightfold significant rise… in 2011 over the average yearly figure of the previous decade,” the study says.

In 2011, whooping cough was more common among adolescents and adults while the reported cases in the previous decade were mainly children and, to a lesser extent, adolescents.

The increase among adults supports a growing international trend that whooping cough is becoming more common among older people.

“The belief that pertussis is chiefly a childhood disease is a common misconception. On the contrary, it is infected adolescents and adults who pose a transmission risk to non-immune infants,” according to the research.

The study was carried out by public health specialist Anthony Gatt, specialist trainees Alexia Bezzina and Amanda Saliba, infectious disease paediatrician David Pace and national immunisation service coordinator Victoria Farrugia Sant’Angelo.

The belief that pertussis is chiefly a childhood disease is a common misconception

Since 2010, Malta’s national health services have offered a series of vaccinations for children against whooping cough. Three vaccines are given: at the ages of six weeks, three months and four months.

When children are 18 months old they are given a combination vaccine that targets whooping cough apart from other infections such as diphtheria, tetanus and polio.

The study points out that while Malta has a high vaccination rate, infections persist as a consequence of waning immunity. Vaccine-induced immunity lasts four to 12 years while naturally-acquired immunity lasts four to 20 years.

“In the absence of further boosting, adolescents and adults (especially mothers) are likely to remain a reservoir of infection and play an important role to transmitting pertussis infection to incompletely immunised or unimmunised infants,” the study says.

For this reason, the researchers recommend having a booster vaccine noting that “feasibility and cost-effective analysis are essential”. Mothers could also be vaccinated before leaving hospital.

The researchers suggest switching the low dose diphtheria, tetanus and polio vaccine given to 16-year-olds to a similar combination vaccine that also includes pertussis.

What is whooping cough?

Whooping cough is a highly contagious acute infection caused by the bacterium bortedella pertussis.

It progresses in stages starting with an irritating cough which, within one to two weeks, becomes increasingly intensified for about two weeks.

This stage is characterised by violent coughing that may be followed by the characteristic whoop or vomiting.

The severity of the cough then tapers off, with an extensive convalescent period that may range between two weeks and three months.

In adults, the manifestations may be less severe and this sometimes leads to it not being diagnosed.

Young babies can be severely affected by whooping cough and it can cause significant damage to their lungs. In adults, complications may include pneumonia and rib fractures.