Whooping Cough

Above: The characteristic "Coccobacillus" shape (stubby rods) of B. Perstussis

Pathogen: Bordetella pertussis (I guess pertussis means "violent cough")

A short history -

• 1906 - Jules Bordet and Octave Gengou are the first to cultivate B. pertussis. This is a very important step as in order to be prove an organism is the etiological cause of disease one must be able to isolate the bacterium in pure culture ( see Koch's postulates).
• 1930s - Development of a "whole-cell" vaccine. The first Bordetella vaccine was essentially killed B. pertussis bacteria. The dead cells were enough to illicit an immune response and cause activation and production of adaptive immune cells.
• 1947 - Childhood vaccination becomes routine. The DTP vaccine (Diphtheria, Tetanus, Pertussis) was very effective (90%).
• 1970s - Concerns about the vaccine arose. Common symptoms included redness, swelling, fever and pain (these are common with almost any vaccine). The main concern was a low frequency of seizures (1/100,00) that was associated but never proven to be caused by the vaccine.
• 1980s - Outbreak of pertussis in Great Britain where mothers were opting out of getting their children vaccinated.
• 1990s - A new vaccine is developed made of purified protein parts of B. pertussis. This vaccine undergoes several different permutations (Tripedia, Infanrix, Daptacel, Boostrix, and Adacel) reaching an efficacy level of 85%. Not quite as effective as original, but fewer side effects.

In the words of E.A. Mortimer, “Some people who go outside after a rainstorm and see frogs believe it rained frogs.” Unfortunately for many parents in Great Britain, the consequences of not vaccinating their children were much higher than the assumed risk of developing "vaccine related" complications. Many children likely died of the following Pertussis epidemic even though the vaccine was never proven to be the cause of any serious complications. Children weren'g vaccinated mainly because of a weak correlation with seizures. This historic example of the "correlation = causation" fallacy (For those who enjoy latin - cum hoc ergo propter hoc) reminds us to be careful about making such false conclusions. It makes sense to err on the side of caution, but it just so happens that the cautious side in this case was to immunize children from a highly virulent and communicable pathogen.