How safe vaccines led to the resurgence of pertussis

For those who haven’t been under a rock recently, several parts of the US have seen a surge in pertussis cases. Much of this has been (fairly) blamed on anti-vaccination efforts to reduce herd immunity and the cocooning of vulnerable infants. But that’s not the whole story.

Interestingly enough, it’s now clear that the DTaP vaccine (diphtheria, tetanus, acellular pertussis) doesn’t provide long-lasting immunity. We had some clues with this as an awareness grew of pertussis in older teens and adults, fueled in part by vastly improved testing for pertussis (PCR versus ‘cough plates’ for culture) and a recognition that pertussis in older kids and adults didn’t look like the classic ‘whopping cough’ that youngsters got.

A booster dose of pertussis vaccine was recommended, included as part of the tetanus booster (the new Tdap vaccines). Recent outbreaks seemed to focus on the group of kids aged 10-11 years of age – when vaccine immunity was waning, but just before their Tdap booster – but the recent outbreak in Washington State has involved even 13-14 year olds, who did get their booster!

The question then should be – why does the NEW vaccine work LESS well? The answer is because it is SAFER.

The old DTP vaccine began to get a bad reputation for neurologic disease – in fact a contraindication still exists to withhold pertussis-containing vaccines in kids who develop neurologic issues after pertussis vaccination, even though the vaccine is different. The old DTP contain literally thousands of antigens, based as it was on a relatively impure cocktail of cell culture fragments that contained the pertussis bacteria. It caused a fair amount of immune reaction, and clearly was linked to febrile seizures.

Several high-profile cases of apparently neurologically damaged children (leading to the formation of some of the early modern anti-vaccine movement) pushed the vaccine manufacturers to create a cleaner vaccine, an ‘acellular’ pertussis vaccine, which is why we have DTP and DTaP. DTaP doesn’t have the same link of febrile seizures and no link to any neurologic issues (interestingly, as detailed in Paul Offit’s book on the history of antivaccine junk science, neither do any of the original DTP kids…it was all a big screwup). Tdap is even less immunogenic as it has slower concentration of antigens – you can tell this because it has a small “p” instead of a big “P”. True story.

The trouble of course is that by having a less inflammatory response, with far fewer antigens, the protection is less. The original DTP vaccine contained more antigens than the ENTIRE modern vaccine schedule does, several times over. Any statement about ‘too many too soon’ is pure bunk – our kids are exposed to fewer vaccine antigens in their entire schedule that we were in one vaccine.

This story highlights several points – firstly, contrary to antivax propaganda, not only are there mechanisms in place to detect and respond to potential vaccine side effects but there are CHANGES made to the vaccines in an attempt to keep people safe. (Probably the only positive thing to come out of the antivax movement is the establishment of the Vaccine Adverse Event Reporting System, VAERS). Secondly, there are compromises to be made – more effective sometimes also means more side effects, so if you want to lower one you may end up lowering the other.

There is also data from Europe that as the vaccine strains of pertussis wane, there is strain replacement with potentially more virulent strains. So although we are seeing fewer cases, those cases we do see may be more serious (this finding hasn’t yet held true for the US…as far as I know).

Of course the antivax brigade have twisted the story yet again “Whooping Cough Epidemic Caused by Virulent New Pertussis Strain—And It’s the Result of Vaccine” shouted one headline. While technically true it doesn’t really go into the real explanation of WHY…even more impressive, but entirely unsurprisingly to me, the actual article the antivax site uses to support their claim starts with the words “Before childhood vaccination was introduced in the 1940s, pertussis was a major cause of infant death world- wide. Widespread vaccination of children succeeded in reducing illness and death.” which not only proves how disingenuous antivax proponents are, but how stupid they are. The first rule of selective quotation is to use sources that support your argument.

Sadly, those who believe antivax propaganda are not usually stupid – if anything they tend to be more educated than average, and well read. They just read the wrong things. Not everyone can go to medical school after all.

Then again, even that isn’t foolproof. One of the original antivax “Expert” witnesses from the UK trials that showed the DTP link with neurologic illness to be wrong went on to further his infamy with AIDS denialism.

Much of the details on the stories of the DTP and DTaP history are in Paul Offit’s book – Deadly Choices, which I highly recommend. In it he not only details how antivax proponents twist science and the facts to suit their case, but also how they nearly brought down the entire US vaccine industry through irresponsible and indefensible litigation. The vaccine WORKS to reduce serious illness from pertussis and undoubtedly saves lives. It’s not perfect, no one has ever said a vaccine was perfect – at least, not unless they were trying to make a point that it wasn’t…

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