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[–] axolotl__peyotl [S] 0 points 7 points (+7|-0) ago 

Pushing Pertussis

The first pertussis vaccine was introduced in the 1930's to treat whooping cough.

The recent resurgence in pertussis infections is put down to a combination of waning immunity and new mutations in the pathogen that existing vaccines are unable to effectively control.

The pertussis vaccine has encouraged evolutionary adaptation, permitting virulent vaccine-resistant strains of pertussis to emerge.

People who are vaccinated against pertussis may be silent carriers of the disease and capable of infecting others. For example, baboons vaccinated against pertussis became carriers and spread the disease.

Because people who are vaccinated against pertussis can still spread the disease, herd immunity and eradication are virtually unattainable:

Asymptomatic transmission is the most parsimonious explanation for many of the observations surrounding the resurgence of B. pertussis in the US and UK. These results have important implications for B. pertussis vaccination policy and present a complicated scenario for achieving herd immunity and B. pertussis eradication.

Fully-vaccinated children are still susceptible to pertussis:

Pertussis has increased in the U.S. since the 1980s despite high coverage with pertussis childhood vaccines. Protection from the DtaP series beings to wane after vaccination, contributing to the accumulation of vaccinated individuals who are still susceptible to disease.

Since protection after vaccination wanes within 2 to 4 years, “lack of long-term protection after vaccination is contributing to increases in pertussis among adolescents.”

New strains of pertussis toxins have emerged subsequent to pertussis vaccination:

Global transmission of new strains is very rapid and the worldwide population of B. pertussis is evolving in response to vaccine introduction.

The vaccine is not effective against these virulent new strains:

Vaccines designed to reduce pathogen growth rate and/or toxicity may result in the evolution of pathogens with higher levels of virulence...waning immunity and pathogen adaptation have contributed to the resurgence of pertussis.

Since Pertussis has “no non-human hosts or environmental niche, vaccine-mediated immunity is the most likely selective pressure against Bordetella pertussis.”

Significant changes in B. pertussis populations have been observed after the introduction of vaccinations, suggesting a role for pathogen adaptation in the persistence and resurgence of pertussis.

Pertussis vaccine failures are due to genetic changes in pertussis strains and poor efficacy, not because too many people are unvaccinated.

When the acellular pertussis vaccine (DtaP) replaced the whole cell pertussis vaccines (DTP) in the 1990s, the World Health Organization created an official standard method to define cases of pertussis.

The new definition was excessively restrictive, requiring laboratory confirmation and at least 21 days of paroxysmal cough. As a result, legitimate cases of pertussis were eliminated and the efficacy of the vaccine was artificially inflated.

The universal use of pertussis vaccines has been associated with genetic changes in circulating B. pertussis strains...with DTaP vaccines, genetic change should be a major concern regarding vaccine efficacy.

Acellular pertussis vaccines are designed to protect against pertactin, however, pertactin-negative mutations have emerged in Japan, France, Finland, Australia and the United States.

DtaP vaccination to protect children from B. pertussis increases their risk of whooping cough from B. parapertussis.

B. parapertussis infections contribute significantly to the overall pertussis burden and contribute to the pool of children thought to have vaccine failure.

Another study concluded that "aP vaccination interferes with the optimal clearance of B. parapertussis and enhances the performance of this pathogen," resulting in "an approximately 40-fold increase in B. parapertussis lung colony-forming units."

Pertussis vaccines also do not protect against whooping cough caused by B. holmesii.

The imperfect immunity given by pertussis vaccines is causing outbreaks of whooping cough in highly vaccinated populations:

The fact that populations of B. pertussis may have evolved to circumvent the immune responses elicited by vaccination and to alter their virulence levels raises a number of questions concerning the design and use of future vaccines.