Acellular vaccine stops the right antibodies being made when pertussis eventually strikes.
It looks as if whooping cough, an infection caused by the bacterium Bordetella pertussis, is going to break records in 2024. Cases have increased in number to levels not seen for over 40 years in Europe and North America. Scientists have speculated about the cause, but studies using baboons are now giving us a plausible explanation.
Cases have increased over 20 years.
Doctors have observed a gradual increase in cases of whooping cough over the last 20 years, although counting is not straightforward. Whooping cough usually comes and goes in 3 to 5 yearly cycles. During these last 20 years, testing methods have become more accurate and general awareness has increased. Both these factors could cause an apparent increase, but now we are sure it is real.
The more than ten-fold increase in cases since late 2023 has been so great that nobody can doubt it is real and important. Covid lockdowns probably prevented the current surge happening sooner.
The pattern in different countries in Europe and North America is so similar and strong, and the timing so synchronous, that it is clearly part of a single phenomenon that needs explaining. I have been somewhat sceptical about resurgence because my own research demonstrated massive lack of recognition of the condition. Although my findings are still valid it can no longer be the whole explanation. Cases really have increased, and the most recent baboon research has convinced me, by providing a rational explanation for the phenomena we are observing. The problem lies with the change for whole cell pertussis vaccine to purified acellular vaccines that took place around the millennium.
Baboons get whooping cough like humans.
In 2012 Jason Warfel and a team at the USA Federal Drugs Administration in Maryland, discovered that baboons could be infected by Bordetella pertussis in a similar way to humans, and that their bodies responded in the same way. Up to that time mice were mainly used to investigate details of Bordetella pertussis infection, but mice reacted differently from humans and were not a good model. The baboon and human similarity in respect to pertussis advanced the process of discovery very considerably and the team has published many papers on this topic since then.
On the 15th of February 2024 The Journal of Infectious diseases published a paper by the FDA baboon team. The principal researcher was Dr. Tod J. Merkel. The lead author was Parul Kapil and it was entitled Repeated Bordetella pertussis Infections Are Required to Reprogram Acellular Pertussis Vaccine-Primed Host Responses in the Baboon Model. The rather long and complicated title does not give a sense of the big breakthrough in understanding the paper contains. Here follows my attempt to explain it in non-technical language.
How whooping cough immunity works.
Some background first. When someone who has not had pertussis immunisation gets infected by Bordetella pertussis bacteria for the first time, antibodies are generated over roughly 7 to 10 days that destroy the bacteria in the nose and lungs so that they do no further damage, and cannot be passed on to infect another person. For the purpose of explaining I will describe two distinct types of immunity activity that are going on. A ‘cellular’ type that focuses on bacteria that are damaging cells, and a ‘mucus’ type that focuses on the thin fluid mucus layer that coats our noses and lungs. These two processes, when engaged, have the combined effect of eliminating all the bacteria from tissues and mucus. The immune system automatically records the chemistry involved so it is primed to respond much more rapidly the next time Bordetella pertussis tries to invade.
The first attack by Bordetella pertussis can damage tissue and make toxins before the process I have described is functioning properly, so the symptoms of whooping cough may be experienced in full. But it will not happen again in the same way because now the immune system is primed to respond faster. Bordetella pertussis frequently attacks but usually fails to do much damage as long as the immunity memory is working properly. And importantly, every time it attacks, the immune system is reactivated and the chemistry re-memorised.
The length of time immunity memory persists is different for different diseases. It may be quite short for Bordetella pertussis because when antibodies are measured they seem to get boosted every few years.
The first vaccines were crude whole cell vaccines.
Whole cell pertussis vaccines were introduced in the 1950s. They were made using killed Bordetella pertussis bacteria and induced the same learning pattern in the immune system as the natural infection, but obviously without causing the disease. Unfortunately there were rare complications associated with that type of vaccine, which were a cause for concern, even though it was not usually the direct fault of the vaccine.
Purer acellular vaccines were developed and introduced in the USA in the late 1990s and in the UK in 2004. When compared with older vaccines they seemed equally good at preventing whooping cough and there were far fewer of the feverish reactions that plagued the whole cell types. Acellular vaccines of various types are the ones in use in most developed countries today.
Acellular vaccines do not stop it being passed on.
Some years ago the baboon team discovered that the newer acellular vaccines failed to provide immunity in the mucus coating of the nose and lungs so that although whooping cough was prevented, the bacteria could still be living in the mucus in large numbers for weeks before dying off. In that time it could be passed on.
This meant that healthy people who had had the acellular vaccine could become infected and therefore spread Bordetella pertussis bacteria without realising they were there at all, because the symptoms, if any, would be relatively mild and attributed to a cold virus or similar. Although spreading it would not be a good thing, it could be reasoned that spreading it to a previously acellular vaccine immunised person would be beneficial as it would boost ‘cellular’ immunity, and especially the ‘mucus’ immunity that they were known to be deficient in. But that assumption is wrong.
Acellular vaccines actually impair the normal immune response to pertussis challenge.
This is where the recent February 2024 report creates a shock. By looking at what happens to acellular vaccine protected baboons when deliberately re-infected with Bordetella pertussis, they discovered that the re-activated immune system failed to produce the mucus clearing system until the reinfections had happened at least twice. In other words, being immunised with acellular vaccine corrupts the immune system in such a way that even when the immune system is given the opportunity to activate the mucus clearing system it fails to do so until it has been stimulated several times by new infection of Bordetella pertussis.
If the baboon experience is equivalent in humans, then acellular pertussis vaccine is preventing the development of a proper immune response when there is exposure to Bordetella pertussis, and is only normalised after repeated exposures.
It is very likely that for everyone, remaining immune to whooping cough throughout life depends on repeatedly being exposed to it and having our immune systems re-stimulated without symptoms, or just very mild ones. The same process normally limits the ability to pass it on. But if you have been primed with acellular vaccine it is probable that several repeated exposures are necessary before you stop being able to pass it on. In real life that could take several years in which the potential to transmit the infection is present. That is what the most recent baboon studies are suggesting. And if it is true, it explains the current resurgence well, and according to the paper, implies that the reservoir is in children even though most cases are in teens and young adults.
The bottom-line message is NOT a bad one. The vaccine is safe and effective. The next generation vaccine must avoid this problem.
The acellular vaccines currently in use are safe and effective. When given as recommended in childhood and in pregnancy they very successfully prevent severe illness and deaths. Before pertussis vaccines were available it killed one in every 25 children that got it. This new information about the current vaccine helps to explain the resurgence better and shows where new vaccines to pertussis need to improve.