Vaccine resistance against pertussis (whooping cough)

This falls under the bad news category.

One thing to note, it has taken a long time for a vaccine resistant strain to show up. Vaccines don’t act as selection pressures in the same manner that antibiotics and antivirals do. Antibiotics act as immediate threats to survival, selecting for the mutants in a population that can survive in the presence of an antibiotic. Vaccines functionally increase the number of infectious particles needed to overcome immunity.

Think of it this way, once you start a course of antibiotics, you already have billions upon billions of pertussis bacteria playing pinochle in your snout, pleural cavity (where your lungs are) and elsewhere, and you have probably exposed everybody that lives with you and a majority of people that work or go to school with you. If they have not been vaccinated, or have not received a booster in the last decade or so, they will be infected.

If a person has been vaccinated and has strong immunity from the vaccine, only the bacteria that are already mutated in a manner to evade the vaccine have much of a chance of successfully starting an infection. Some bacteria are better than others at infecting a host, and a smaller number of bacteria are needed to kick off an infection. This is called an infectious dose. The infectious dose of pertussis is probably pretty low, since it is so easily transmitted (susceptible coworkers are 70-90% likely to catch whooping cough, and since kids have terrible hygiene, its even higher for them. Since we don’t know what that dose is, let’s just call it X. If the mutation to evade a vaccine is only present in one out of a million bacteria (a very generous guess), the infectious dose for a vaccinated individual is one million times X. This makes it a lot harder for a vaccine evading strain of a bacteria like pertussis to get started than an antibiotic resistant strain. Luckily, when antibiotic resistant strains show up, they don’t tend to spread very well, probably because the level of vaccination is decently high.


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