Modern view of pertussis infection
Discoveries about the nature of B. pertussis in the the last couple of decades have completely changed our understanding of it. We now know it has a dual 'personality'.
Life number one causes whooping cough, and life number two temporarily invades our nose and throat but causes no symptoms or symptoms that are minor and generally ignored. This second life is hundreds of times more common than the first kind. It is the first life that this website is about. There may be a middle group with symptoms but without any of the characteristic prolonged coughing bouts and prolonged coughing absence that is the mark of clinical whooping cough, but the size of this middle group is speculative.
When B pertussis gets into our bodies it sticks to the little microscopic hair-like fronds (cilia) that line the large air passages and starts to multiply and produce toxic substances that can damage nearby tissues and cause the characteristic cough. If we have no immunity these substances can do a lot of damage and as we know, even kill very young babies. If we are a bit older than that, these substances can give us what we call whooping cough which is very unpleasant and long lasting. But not everyone gets it severely, and some get it hardly at all for reasons that are not understood yet. However, it is so infectious that we will all get infected in childhood or early adulthood if we have not been immunised. Even if we have been immunised we will still get it but probably without symtoms because the immunisation neutralises the toxins. Getting infected boosts our immunity even without symptoms.
The immunity we get from the natural infection does not last long at all but throughout life it keeps getting boosted perhaps every few years by unnoticed reinfection and so we are kept free of the actual whooping cough disease by and large.
The acellular vaccines that are current in use, and have been for about 20 years, do not give protection for as long as the old whole cell vaccine or the natural infection and do not stop the pertussis bacteria reproducing in our airways and possibly passed on. That may be why there seems to be more whooping cough about.
Much effort is being directed at producing improved vaccine but it may be many years off.
We need to get an understanding of why it becomes severe in some people but not most, when it reinfects.