Does Tdap Protect You From Whooping Cough?

Within the past few years an epidemic of whooping cough swept through and injured youngsters in California and Arizona. There were tragic childhood mortalities in the frail not yet vaccinated pediatric population. The researchers from the Center for Disease Control and National Institute of Health swooped in and concluded that adults, primarily grandparents, were transmitting the disease to their newly arrived and not yet immunized grandchildren. They reasoned that the adults’ immunity from their childhood vaccinations with DPT had worn off and they were unknowingly transmitting it to the youngsters after a mild adult upper respiratory tract infection with bronchitis.  We were told that in adults, Bordetella pertussis produced bronchitis indistinguishable from a viral bronchitis. This was just the type of illness health care leaders were telling physicians not to prescribe an antibiotic for in their international campaign for the prevention of antibiotic resistance developing.  Little did they know at first that in adults, the bronchitis is a mild illness but in children it is aggressive and is often lethal.  They were not originally aware that long after our adult mild bronchitis resolved we could still transmit the bordetella pertussis to our grandchildren.

Their solution was to re-immunize adults with a pertussis booster in combination with your next tetanus shot. The combination was called Tdap.  A national information campaign was undertaken to get primary care physicians to spread the word to their adult patients.  The question is does it really work? In a recently published study led by Dr. Nicola P. Klein of the Kaiser Permanente Vaccine Study Center in Northern California which appeared in the Journal Pediatrics, it seems that the vaccine is only effective for a short time in the very healthy and robust 11 and 12 year children.  Their study showed that Tdap protected young adolescents 69% of the time in the first year, 57% in the second year, 25% in the third year and only 9% in the fourth year.  The vaccine was given during an epidemic in California in whooping cough in the hopes of averting a greater infection rate.

 

The failure of the vaccine to provide long term benefits in adolescents and teenagers will lead to different immunization strategies. Tdap is already a milder form of a former vaccine, scaled down to prevent some of the rare side effects seen when it was administered.  A possible return to that previous vaccine or whole cell preparation may be needed. Another proposal calls for vaccinating pregnant women hoping that their maternal antibodies will pass to the fetus and provide long term protection.

The real question with no answer is what about the millions of adults who received Tdap with immune systems far less robust and protective than adolescents?  Are they immune and for how long?  No one knows because the research has not been done or published yet.  Still the CDC and the NIH and the American College of Physicians call for adult immunization with Tdap.  The Kaiser Permanente Study will surely establish the need for an adult efficacy investigation. Until then we will give the Tdap while we wait for answers. It does raise the question of whether our approach to adult bronchitis should include an antibiotic that treats Bordetella pertussis until a quick test is developed to distinguish it from run of the mill viral pneumonias.

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