What’s behind the uptick in cases of whooping cough?
A quick survey of the news and media produces daily warnings that pertussis (whooping cough) is on the rise. These sources often blame low vaccination rates or under vaccination. However, that leaves out other important possible factors while stigmatizing parents that choose, for a variety of reasons, not to vaccinate their children.
For instance, researchers have recently found vaccine-resistant strains of bordatella pertussis (the bacteria that causes whooping cough) in the U.S. Researchers analyzed 30 samples of bordatella pertussis specimens from children hospitalized in Philadelphia and found 60% were a variant resistant to the vaccine. The current pertussis vaccine relies on pertactin (a protein on the outer membrane of the bacteria) as an antigen. Meanwhile, the study revealed the pertussis bacteria has developed at least two variants that halt the production of pertactin. This means the immune system, which has developed immunity from the pertussis vaccine, does not recognize the mutated pertussis strain. French studies of pertactin-negative mutated strains have shown that such strains are just as infectious as non-mutated strains.
Another cause of the uptick in cases of pertussis is related to the waning immunity provided by the DTaP vaccine administered to children. Studies have revealed that the protection from the fifth dose of DTaP (usually administered between 4 and 6 years old) decreases substantially during the five year period following vaccination.
Finally, a recent study suggests that people vaccinated against pertussis are still able to spread pertussis. Scientists exposed baboons (those that had been vaccinated, unvaccinated, and previously exposed) to pertussis. Baboons that were previously exposed (sick with) pertussis did not become sick again, and there was no germ growth in their throats. Unvaccinated baboons exposed to pertussis became sick. Baboons that had been vaccinated did not display signs of being sick; however, there was germ growth in their throats, and they harbored the germ for 35 days.
In another test, vaccinated baboons were exposed to pertussis and placed in cages two days later with baboons that had not been vaccinated and not previously exposed to pertussis. In each case the vaccinated baboon spread the pertussis to their cage mate who developed pertussis. If vaccinated people can still spread the bacteria while being asymptomatic, the effectiveness of “cocooning” new infants, which is vaccinating the people who are in contact with infants, is called into question.
While none of the above causes and potential causes can solely account for the supposed rise in cases of whooping cough, all of them could explain why more cases are occurring and why whooping cough has been reported in fully vaccinated people.