Just wanted to clarify.

One does not get lifelong immunity from pertussis vaccination.  Ironically
pertussis is not an uncommon disease in adulthood-chronic cough of extended
duration should alert providers to considering the diagnosis).  It is
generally underdiagnosed by providers seeing adults.  Also as it is difficult
to diagnose (very difficult to culture, blood serologies take a long time) it
is generally diagnosed clinically.  All that sounds like a whoop may not be
(can be mycoplasma, other organisms such as B parapertussis, Chlamydia
trachomatis, Chlamydia pneumoniae, B bronchiseptica and possibly, certain
adenoviruses can give one similar illnesses)!  Fortunately with the exception
of adenoviruses all the other organisms are susceptible to the same class of
antibiotics (macrolides- erythromycin, biaxin-tastes awful and zithromax).

From the 1997 Red Book, American Academy of Pediatrics, pp 394-3995

Humans are the only known hosts of B pertussis.  Transmission occurs by close
contact via respiratory secretions of patients with disease. Asymptomatic
infection has been demonstratied but is unlikely to be a major factor in
transmission.  Pertussis occurs endemically with periodic outbreaks.  As many
as 90% of nonimmune household contacts acquire the disease.  Adolescents and
adults reecently have been recognized as major sources of pertussis,
accountaing for as many as 25% of reported cases in recent years; infants and
young childdren are frequently infected by older siblings or adults who often
have mild or atypical illness.  While pertussis can occur at any age,
approximately 35% of reported cass currently occur in infants younger than  6
months inculding a substantial proportion in those younger than 3 months, and
approximately 60% oppour in children younger than 5 years.  Infants bourn
prematurely are especially at increased risk of severe pertussi, resulting in
hospitalization and including death.  Widespread immunization with pertussis
vaccine since the 1940's his primarily responsible for the current low
morbidity and mortality  rates of pertussis in the United States.  Patients
are most contagious during the catarrhal stage before the onset of
p[aroxysms; communicability then diminishes rapidly but  may persist for 3
weeks or more after onset of cough."

Hope this helps!

Keep on washing those hands -it really makes a difference (for a plethora of
communicable diseases).

Pierrette Mimi Poinsett MD FAAP
Modesto CA