The Netherlands has been vaccinating the population against whooping cough since 1957
Older children have more antibodies against the whooping cough bacteria than younger children, because they are exposed to the pathogen more often. They also show a stronger immune response after a booster vaccination against whooping cough. Exposure is therefore an important factor in the timing and effectiveness of vaccines. This is evident from a publication by Radboudumc in Nature Communications.
The Netherlands has been vaccinating the population against whooping cough since 1957. That’s the ‘K’ in the DKTP vaccination, which children receive three times in their first year of life, and again when they are four years old. Yet the bacteria that causes whooping cough is still going around and making many people sick. This is because the vaccines protect very well against serious illness, but less well against infection with the highly contagious whooping cough bacteria.
What is the effect of pertussis bacteria circulation on a booster vaccination? Immunologist Dimitri Diavatopoulos and PhD student Janeri Fröberg of Radboud university medical center wondered that. They examined two groups of children. ‘One group was between 7-10 years old, the other between 11-15,’ says Fröberg. ‘They had all received their series of injections from the National Immunization Programme. We gave them a booster and looked at the immune response in the nose, before the booster, and a month and a year after that. In our measurements we distinguished between antibodies against the vaccine and against the bacteria itself.’
sick reports
The first thing that stood out was that the older group of children already had more antibodies against the whooping cough bacteria in their noses before the booster vaccination than the younger group. “That could be due to exposure to the bacteria,” says Diavatopoulos. ‘Older children have had longer time to come into contact with the bacteria themselves. But whooping cough outbreaks are often very local, so exposure can vary greatly per region and age group.’ To check this, the researchers delved into the regional data on whooping cough sickness reports, made available by the RIVM. ‘We did indeed see more sick reports due to whooping cough among the older group.’
Second, the researchers studied the response to the booster vaccination. Fröberg: ‘In the group with older children, we saw more antibodies in the nose against the vaccine, and a slower decrease in antibodies from one month to one year after the booster. That is a very interesting finding. It could mean that exposure to the pathogen leads to long-lasting antibodies in the nose after a booster vaccination, and thus possibly protection against the disease. Conversely, an additional vaccination without exposure may result in a less strong immune response.’
Insight
The degree of exposure to a pathogen appears to be important for the response to a vaccine, with possible consequences for the vaccination programme. ‘Different countries vaccinate against whooping cough at different ages, and the number of booster vaccinations also varies,’ explains Diavatopoulos. ‘In the Netherlands we give children a booster at the age of four, while in other countries this is done, for example, with children aged nine or twelve. In our vaccination program, that shot will soon also shift, from four to six years old. Our study supports this subsequent administration of a booster. We must take into account the right balance between the circulation of the bacteria and the severity of complaints in people who become infected. A little exposure can be beneficial for the effect of the vaccination, but the burden of disease must remain sufficiently low.’
That vaccines protect well against disease, but are less effective against spreading, we have heard that more often in recent years. “We see parallels with the corona pandemic,” explains Diavatopoulos. ‘There too, the immune response is an interplay between vaccination and exposure. The sum of these factors influences how well a vaccine works and to what extent you are protected. As far as I’m concerned, we will take exposure into account in every study into a new vaccine, which will give us much more insight into protection.’
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