Friday, March 8, 2019

The Skinny on Pertussis, Vaccines and Enforced Mandates

Meryl Nass, M.D.
March 10, 2019

Pertussis is a common bacterial infection that is uncommonly diagnosed, with probably over a million cases yearly in the US.  Worldwide there were an estimated 24 million cases, per CDC.[1]

"The confirmation of Bordetella pertussis infection is still one of the most difficult diagnostic challenges facing the clinician, particularly in adolescents and adults"--from the textbook Vaccines."[2]

A 2006-7 survey in the Netherlands suggested that 9% of those over age 9 had had pertussis in the past year.[3]  Other studies suggest that up to 26% of those seeing a doctor for chronic cough had pertussis.  The bottom line is that because it is hard to get a precise diagnosis, we do not really know how common pertussis is.  But it is common. 

It is common because neither the disease nor the vaccine confer much immunity.  During the first year after a Tdap vaccination, effectiveness is estimated about 67%, but by 4 years later effectiveness may be only 9%.[4]  The WHO says,

The disease, caused by the bacterium Bordetella pertussis, is endemic in all countries. Epidemic cycles have been occurring every 2 to 5 years (typically 3 to 4 years), even after the introduction of effective vaccination programmes and the achievement of high vaccination coverage.[5]

Pertussis circulates within the US at all times.[6] 

Pertussis causes a respiratory illness with cough that can last several months. There are about 10 deaths yearly from pertussis in the US.[7]  It is most dangerous in young infants, who are most likely to be infected by their older, previously vaccinated siblings.

Of children diagnosed with pertussis aged 6 months to 6 years, only 10% had received no pertussis vaccinations.[8]

The only pertussis vaccines available in the US are the DTaP (for small children) and Tdap (for those older than age 7).  Each contains toxoids and antigens for 3 diseases:  tetanus, diphtheria and pertussis.  There is no individual pertussis vaccine.

DTaP is recommended as a 5 dose series beginning at 2 months of age.  Tdap (which surprisingly contains considerably lower doses of diphtheria and pertussis toxoids/antigens and (in one brand) tetanus toxoid, is recommended as a single dose for 12 year olds, or for older individuals who have not yet received it.  It is recommended (off-label) for pregnant women during the latter part of every pregnancy, although it has not been proven safe for them.[9]  The idea was to provide maternal antibodies to newborns this way.

Yet the WHO noted: [10]

Pertussis remains an important cause of infant death worldwide and continues to be a public health concern even in countries with high vaccination coverage. Maternal antibodies do not appear to protect neonates from severe pertussis, and even for individuals with vaccine-induced immunity, the initial antibody-mediated immune response to B. pertussis may minimize the toxic damage to both epithelial and immune cells, but it has limited impact on its subsequent circulation among non-immunized children and older individuals with waning immunity.

In plainer language, this means two things:
  1. 1)  that vaccinating pregnant women to induce maternal antibodies is unlikely   to prevent severe pertussis in their exposed neonates, and
  2. 2)  that while recent vaccination is protective against pertussis disease,   because of short duration of protection, herd immunity can never be   achieved.

Furthermore, it is now known that the vaccine confers protection against pertussis symptoms, but fails to prevent infection by pertussis bacteria.  It seems hard to believe, but CDC acknowledges this is the truth, below.  The result is that vaccinated people are likely to spread pertussis, because of the absence of significant symptoms.

From CDC's 2018 pertussis recommendations:[11]

Studies in animal models have shown that acellular pertussis vaccines protect against disease but not against infection or transmission of B. pertussis or the closely related species, B. bronchiseptica....

... recent evidence suggests that vaccination with acellular pertussis vaccines does not prevent transmission and therefore does not afford indirect protection against pertussis

In contrast to tetanus and diphtheria, the incidence of reported pertussis in the United States has been increasing despite high infant and childhood coverage with DTaP vaccines and increasing Tdap coverage among adolescents

And yet another problem: an FDA study found that vaccinated baboons who were then exposed to pertussis developed asymptomatic illness, and spread infection much longer than unvaccinated animals.[12]

It should be apparent that how pertussis vaccinations impact the spread of pertussis is unsettled.  In a tacit acknowledgement of this, CDC responded to the issue of pertussis transmission in the healthcare setting, but realized there was little they could offer. Among CDC's points to consider:[13]

·       "Vaccinating healthcare personnel with Tdap is not a substitute for infection prevention and control measures including post-exposure antimicrobial prophylaxis.
·       There is no supportive evidence that additional Tdap doses would prevent pertussis disease and transmission in a healthcare setting.
·       Vaccine effectiveness studies suggest the duration of protection against pertussis afforded by Tdap vaccination in adolescents is less than 4 years
·       Despite high Tdap coverage and recent receipt of the vaccine, adolescents are experiencing high rates of pertussis in the United States.

Clearly, if extra pertussis vaccinations will not prevent pertussis in hospitals, they will not prevent them in schools, or anywhere else.

We need better vaccines.  We need safer vaccines.  A captive market has allowed vaccine manufacturers to avoid developing products that work as expected.  

Strict mandates will not only disincentivize improvements to vaccines, but open the door to newer, unsatisfactory vaccines being added to the childhood schedule--and we will have no choice to refuse them.

[2] Edwards KM and Decker MD. "Pertussis" in Vaccines, edited by Plotkin SA et al., 6th edition. 2013.

1 comment:

Ignatius Albright said...


It's so good to see you back and posting again! Either you've been really busy starting your business, or very little has gotten under your skin in the past year :-) I'm glad I still check this now and then to see if you're still posting. I've missed you and I suspect others have as well!