Diptheria- Who is at risk?
Tetanus- Who is at risk?
Pertussis- Who is at risk?

An InsideVaccines blog entry about pertussis

Click here to read all about what the pertussis vaccine does (or doesn’t, as the case may be) do in terms of herd immunity.

What does pertussis “look like” in unvaccinated infants and children?

Manufacturer’s Inserts and efficacy statements:

Daptacel– Efficacy of the DTap ranged from 59-89%.
  The Tetanus portion of the vaccine has never been tested for efficacy.

Interestingly, the CDC’s Reported Cases and Deaths from Vaccine Preventable Diseases,United States, 1950-2005 shows Pertussis cases at the highest reported rates since 1959. (Vaccine became available in the 1940s).

In the Journal of Theoretical Biology they discuss the failure rate of the pertussis vaccine in New Zealand.

The obtained figures indicate that in New Zealand the effective vaccination rate against pertussis is lower than 50%, and perhaps even as low as 33% of the population. These figures contradict the medical statistics which claim that more than 80% of the newborns in New Zealand are vaccinated against pertussis (Turner et al., 2000). This contradiction is due to the mentioned unreliability of the available vaccine. The fact that the fraction of immune population obtained here is considerably lower than the fraction of vaccinated population implies a high level of vaccination failure.

The Official Journal of the American Academy of Pediatrics addresses the issue of investigator bias affecting efficacy trials.

In the course of a large pertussis vaccine efficacy trial we realized that investigator compliance could have a major impact on calculated vaccine efficacy.

Conclusions. Our data suggest that observer compliance (observer bias), can significantly inflate calculated vaccine efficacy. It is likely that all recently completed efficacy trials have been effected by this type of observer bias and all vaccines have considerably less efficacy against mild disease than published data suggest.

A study completed on vaccinated children in Israel concluded that the pertussis vaccine does not prevent transmission, it merely prevents the subjects from getting or feeling ill. (So it makes the pertussis infection subclinical).

Vaccinated adolescents and adults may serve as reservoirs for silent infection and become potential transmitters to unprotected infants (3-11). The whole-cell vaccine for pertussis is protective only against clinical disease, not against infection (15-17). Therefore, even young, recently vaccinated children may serve as reservoirs and potential transmitters of infection

Granted, we are using the acellular pertussis now in the US, but it’s widely acknowledged that the whole-cell was in fact more efficacious (but more reactive). So, even this vaccine which “worked better” than what we are currently using, didn’t prevent transmission/infection. It prevented the symptoms.

Interesting discussion of how the pertussis toxin prevents/delays appropriate antibody response, thus allowing infection of immune hosts.

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