Whooping Cough Vax question

[splunky]

I have 4 children (ages 10-2), ds1 and ds2 have been fully vaxed up to age 5 Ds3 has been vaxed til age 2. DD has had none.
Ds1 and dd had what I beleive to be Whooping Cough! Ds1 had the vaccine but must have worn off, as "they" believe is now happening, I think, between the ages of 11-14.
Ds2 and ds3 never got the full blown thing, but had coughs to varying mild degrees along with sniffles ect.
My question is, since they were exposed, although they had the vax, is thier(ds2 & 3) immunity boostered from this? Or when thier vaccine wears off they will be totally susceptable again?
Also, now that Ds1 and dd have had it, how long is their immunity good for? Is it a case of once you have had it you are good, or do you need to be exposed again, kinda like Chicken Pox?

You know, getting the Ped to admit this is what is was, was like pulling teeth! She just kept saying "well, he had the vaccine". She still didn't actually say the words, of that was what it was. But when I told her of myresearch etc, she agreed it was very likely and why ds 2 and 3 didn't get it. Ugh!

[mamakay]

Yes, you need to be periodically re-exposed to WC to stay immune, but it's so common that most people catch a subclinical case every 3-5 years or so. When you get a really obvious case is when you go a long time without exposure, and then catch it again.

This is a really interesting fulltext...I recommend reading the whole thing...

http://pediatrics.aappublications.or...ull/115/5/1422

Household-contact studies have indicated that infection without illness is common.40,41 These data suggest that frequent exposures maintain antibody levels in many persons at protective levels. Illness only occurs when antibody values have fallen below critical values, and then exposure occurs.