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Old 03-20-2009, 12:01 AM
 
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Originally Posted by serenitii View Post
However, serodiagnosis of H. influenza type b infections might be limited to older children and adults, since it has been found that most young children do not respond with antibody formation either to natural H. influenza infections or to vaccination with purified capsular polysaccharide (12-14). The children with H. influenza infections included in this study (even the 6-month-old child) showed specific antibody responses. Furthermore, it is known that several types of bacteria possess antigens which cross-react with type b polysaccharide (5,18) (e.g., E. coli K-100 [15], pneumococci [19], and other bacteria [1]). Therefore, it is conceivable that such organisms could give rise to antibodies that cross-react with H. influenza type b polysaccharide, which might explain the initial titers, in addition to previous H. influenzae type b infections.
2 of the three studies are looking at the response to the vaccine.
This is the only fulltext I could find.
http://www.pedresearch.org/pt/re/ped...97303000-00001

There was one study that looked at natural infection, but they didn't break it down by age in the abstract. Even assuming that study does show in the fulltext that the infants under 2 didn't respond, we're still 2:1 on studies favoring natural immunity happening in infants. 3:1 if we count the study I just linked to, where they observed an infant form antibodies after asymptomatic carriage.
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Old 03-20-2009, 01:45 AM
 
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Originally Posted by mamakay
There was one study that looked at natural infection, but they didn't break it down by age in the abstract. Even assuming that study does show in the fulltext that the infants under 2 didn't respond, we're still 2:1 on studies favoring natural immunity happening in infants. 3:1 if we count the study I just linked to, where they observed an infant form antibodies after asymptomatic carriage.
Could you sum up the studies for reference?

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Old 03-20-2009, 02:00 AM
 
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To complicate it even more...

http://www.pubmedcentral.nih.gov/pic...8&blobtype=pdf

Quote:
The pioneering study of Fothergill and Wright (3) showed that immunity to Haemophilus influenzae type b (HIb) was age-related and associated with bactericidal (BA) antibodies. These BA antibodies were assumed to be protective against disease and were subsequently shown to be directed primarily at the HIb capsular polysaccharide antigen (1, 23). However, several lines of evidence have suggested that anticapsular (AC) antibodies are not solely responsible for protective immunity to HIb.
ETA:

It is this study by Fothergill in 1933 that established the consensus of age related immunity: http://www.jimmunol.org/cgi/content/abstract/24/4/273 The text of this paper is where that chart showing the bactericidal activity of blood came from (it was actually copied from the paper.)

This references it as well:

http://emedicine.medscape.com/article/1164916-overview

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Transmissibility of Hib infection and the capacity of this organism to cause purulent meningitis was first demonstrated by Wollstein in 1911. She first drew attention to the marked tendency for Hib meningitis to occur in infants and young children. Pittman distinguished 6 serotypes (A through F) of H influenzae in 1931 and demonstrated that the B serotype accounted for almost all cases of meningitis. Fothergill and Wright enlarged the epidemiologic understanding of Hib meningitis, the protective role of passively transmitted maternal antibodies, and the inadequacy of host immune response from infancy to age 3 years in an important series of studies published in 1933
Also, reading further down in that last link:

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Hib meningitis is quite rare in the first 2 months of life, accounting for 0-0.3% of all meningitis cases in this age group. Children of this age group are likely protected from infection by the passive transfer of maternal antibodies. These antibodies are considerably diminished by 2 months of life and are often completely gone by 4 months of life. This period of limited vulnerability appears to be prolonged in breastfed infants, likely because of continued passive transfer of antibodies. This effect is thought by some authorities to account for the fact that young children who develop Hib meningitis in Northern Europe do so at an older average age than children who develop Hib meningitis in North America. These authorities suggest that more Northern European mothers engage in breastfeeding of infants and that they tend to do so for longer periods than North American mothers.

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Old 03-20-2009, 04:41 AM
 
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Originally Posted by mamakay View Post
So...why did it that happen there, but not in the US? Different vaccine? You'd think it would have already happened here if it was going to, but both Hib carriage and invasive disease are at an all time low in the US in adults. Or could it be the fact that we (generally, not sure about the Netherlands) do an extra booster dose or two?
Could doing too few shots in the series have allowed circulation in kids to have continued (albeit at a lower level than prevax), and there's where the selective pressure for genetic diversity came from?
http://ecdc.europa.eu/documents/pdf/...032004_hib.pdf

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Despite the high reported vaccine effectiveness of Hib conjugate vaccination, a resurgence of Hib disease has been seen in both UK and, to a smaller extent, Netherlands. The rise in the former, which began in 1999, about seven years after introduction of Hib conjugate vaccination, peaked in 2002, and was ascribed to a combination of factors. These included waning immunity in the absence of a booster dose in the second year of life, and use of acellular pertussis vaccine, which has been associated with lessened immunogenecity of the Hib component. Neither of these conditions apply to the Netherlands, which saw a sudden increase in Hib incidence in 2002, 3-fold greater than that seen in the 6 previous years and that has been sustained in the years following. It has been suggested that changes in population immunity may be the most important factors in both countries. For example, reduction of Hib carriage in children caused by Hib conjugate vaccination has resulted in a lack of natural boosting of immunity in adults. This in turn has led to accumulation of susceptibles sufficient to allow increased Hib transmission and thus a much greater level of exposure to potentially invasive Hib strains by highly susceptible individuals. There is evidence of an abrupt increase in the genetic diversity of Hib strains after introduction of the vaccine.
If this is the most important factor -- then, are we headed for an increase for the same reasons?

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Old 03-20-2009, 05:38 AM
 
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Originally Posted by serenitii View Post
http://ecdc.europa.eu/documents/pdf/...032004_hib.pdf



If this is the most important factor -- then, are we headed for an increase for the same reasons?

Quote:
For example, reduction of Hib carriage in children caused by Hib conjugate vaccination has resulted in a lack of natural boosting of immunity in adults. This in turn has led to accumulation of susceptibles sufficient to allow increased Hib transmission and thus a much greater level of exposure to potentially invasive Hib strains by highly susceptible individuals. There is evidence of an abrupt increase in the genetic diversity of Hib strains after introduction of the vaccine.
We could be...

I wonder if the CDC will think to start doing large Hib carriage studies in adults here?
With the recent "outbreaks", I'm also not sure we're not on the receiving end of selective reporting. But we won't know for 18 months or so if the apparent increase is real.
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Old 03-20-2009, 06:05 AM
 
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Originally Posted by mamakay View Post
We could be...

I wonder if the CDC will think to start doing large Hib carriage studies in adults here?
With the recent "outbreaks", I'm also not sure we're not on the receiving end of selective reporting. But we won't know for 18 months or so if the apparent increase is real.
They should... and now but why do I doubt that will happen until retrospectively? Carriage in the adult population was very low in the pre-vaccine era. I bet that isn't the case any more. In fact, it could be this change in reservoir that allowed the relatively minor vaccine shortage to create the "outbreak" (if it is indeed a real one.)

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Old 03-22-2009, 11:40 AM
 
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I am now sooo neck deep in this vax issue, it's been taking over every spare moment I have for the past 3 weeks. I feel like I NEED to decide very very soon on what to do. I talked with a organic food store owner today about vaxing (she doenst vax) and ended up getting rather teary. !! I just havne't really talked face to face about this issue with another "crunchy" mama who understands how emotions/mama instinct are part of this decision...

I am SOOO right where you're at.

Jen, mom of  two amazing girls, b. 2/16/06  and 1/29/10 hbac.gif

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Old 03-25-2009, 12:18 PM
 
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OK, I've read the whole thread here. I'm looking into delaying vaccination here.

It sounds like, from what I am reading here, that vaccinating with hib prior to 2-3 years old may be meaningless as it seems to show no immune response?

So, if that is true, what is the point in doing the vaccine prior to 2-3 years old?

And, that breastfeeding has a protective effect.

Is that correct?

I'm troubled too, reading about the vaccinations and how it is completely altering how the immunity between adults/children, etc.
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Old 03-25-2009, 12:25 PM
 
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There are some really good stuff on the dr sears page on this as well as some good info in his discussion section going on right now and a few pages back. I recommend the read there as well.

"Parents are simply trustees; they do not own the bodies of their children"-Norm Cohen  Martial arts instructor intactlact.gifhomebirth.jpgnak.gif and mom to 4: DD1 (1/05) DS (7/06) DD2 (5/08) DD3 (2/11)
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Old 03-26-2009, 06:31 AM
 
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Originally Posted by paisleypowell View Post
It sounds like, from what I am reading here, that vaccinating with hib prior to 2-3 years old may be meaningless as it seems to show no immune response?
No, that is not the case. The lack of ability in children under three to fight Hib well seems to be a general consensus in the scientific community. After some digging, this was demonstrated in a pioneering study in the early 1900's. They basically took blood from kids of different ages and tested how many bacteria it could kill in a lab setting. Ultimately, they correlated the high incidence of invasive Hib in certain age groups (under 5, but really more-so under 2 or 3) with the inability of the blood in that age group to kill the organism.

This is all in no way related to a child's ability to mount an immune response to the conjugated vaccine. The conjugate vaccine works very well. The question is, are the risks of the vaccine worth the benefit? The benefit, of course being protection against Hib. The risks being: 1) Short term reactions (this vaccine does have one of the more "safe" profiles, at least.) 2) Long term risks (The jury is out on this one. There is the issue of serotype replacement. Also, some evidence has been given that Hib may be connected to a risk of Type 1 Diabetes, but this has generally been refuted. I haven't dug into this yet to know the details.)

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Originally Posted by paisleypowell View Post
And, that breastfeeding has a protective effect.

Is that correct?
Yes, breastfeeding has a protective effect. Breast milk has lots of antibodies, especially, IgA antibodies which protect mucosal linings and do all sorts of other good things.

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Originally Posted by paisleypowell View Post
I'm troubled too, reading about the vaccinations and how it is completely altering how the immunity between adults/children, etc.
The scientific community, in general, thinks it is a good trade-off. And likely, they'll continue to fight any fires they create after-the-fact with more vaccines.

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