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Immunity after one dose?

post #1 of 9
Thread Starter 
I have another thread on the go regarding my unique situation.

Someone mentioned the possibility of having immunity after 1 dose of the DTaP.

Does anyone have a good understanding of how immunity and boosters work? (specifically with DTaP & HiB)

Is it possible that my son could have enough immunity after 1 dose of the DTaP (it's combined with HIB, and Polio here)

I'm going to do a little digging for info too, please feel free to send me links...
post #2 of 9
The boosters and second doses work in two ways:
Some are meant to catch people who weren't immune after the first dose. Others are to boost or restore waned immunity.

I don't know which is the case for those vaxes.
post #3 of 9
I think the primary series (first 3 or 4, I think 4, for dtap) is meant to increase the % of kids who responded to the pertussis part. Since immunity wanes so fast for pertussis, another dose is needed around 4 or 5, and then every few years, to keep the level of antibodies up (for pertussis, specifically, I mean). Kids who are breastfed create more antibodies with fewer exposures to the vaccines (I think for all vaccines, not just pertussis), not sure if there are other factors as well. But even with pertussis, which is the worst of the lot in terms of % responding at first, I think it's over half of kids who respond to the first dose (I am thinking in the 60% range but I have no idea where I read that).

I don't remember about Hib, I crossed it off my list much sooner than pertussis.
post #4 of 9
I was just at the pedi a few hours ago and asked your question (I wanted to know too as we were "scheduled" to have the 2nd dose of DTaP and I wasn't sure I wanted to). She said the repeat doses are necessary to maintain the immunity. Babies may get immune from shot #1 but the titers tend to decrease after a few months until you've had 3 or 4 doses. And even at that boosters are needed again - Pertussis immunity seems to wear off more than the other diseases we vax for.

Anyhow, FWIW I went ahead with booster #2 b/c even though Pertussis is very unlikely to cause a fatality in my 10 month old it can cause long-term damage to the lungs. My DH's grandmother had it as an infant and has had life-long asthma which she attributes to the disease. And since it is fairly common in the end I opted for it.
post #5 of 9
Thread Starter 
Helpful....thank you!!
post #6 of 9
yeah, I want to know this about hib? any immunity after one dose?
post #7 of 9
With most shots, they don't do actual effectiveness studies with kids who only get one or two doses. So there's really no telling.
With pertussis, they don't even have a "correlate of immunity" (how much antibody is thought to provide protection) AND they're not even sure which of the 5 "parts" of the vaccine even have an actual effect in lessening disease severity.
That said, they did come up with a "guesstimate" on the "correlate of immunity" and they have tested kid's blood, and, iirc, about 90% met what they thought should qualify as protection after one dose. But there's a LOT of guesswork going on there.
So it's really one of those vax issues that's unknown.

I'm not sure if they've ever checked with Hib. I think one dose is considered enough if given after age 2, but I bet they decided that back when Hib was endemic, so a dose given after age 2 would just be building upon immunity that was already there from "natural" exposure from colonization.
post #8 of 9
Here's the pertussis study.

But...remember, those immunogenicity tests are really just guesses, especially with pertussis.

post #9 of 9
This Hib vax package insert shows seroconversion after one and 2 doses...


But they also say:

An important virulence factor of the Hib bacterium is its polysaccharide capsule (PRP).
Antibody to PRP (anti-PRP) has been shown to correlate with protection against Hib disease.3,21
While the anti-PRP level associated with protection using conjugated vaccines has not yet been
, the level of anti-PRP associated with protection in studies using bacterial
polysaccharide immune globulin or nonconjugated PRP vaccines ranged from >0.15 to
>1.0 mcg/mL.22-28
That's a guess, too...
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