The prevaccine Hib estimates - Mothering Forums
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Vaccinations > The prevaccine Hib estimates
mamakay's Avatar mamakay 05:27 AM 03-05-2009
Here's where it comes from.

It's 1985, and the CDC is gearing up to introduce the old, crappy hib polysaccaride vax.

http://www.cdc.gov/mmwr/preview/mmwrhtml/00022818.htm

Quote:
April 19, 1985
Several population-based studies of invasive Hib disease conducted within the last 10 years have provided estimates of the incidence of disease among children under 5 years of age, the major age group at risk. These studies have demonstrated attack rates of meningitis ranging from 51 cases per 100,000 children to 77/100,000 per year and attack rates of other invasive Hib disease varying from 24/100,000 to 75/100,000 per year (1). Thus, in the United States, approximately one of every 1,000 children under 5 years of age develops systemic Hib disease each year, and a child's cumulative risk of developing systemic Hib disease at some time during the first 5 years of life is about one in 200. Attack rates peak between 6 months and 1 year of age and decline thereafter. Approximately 35%-40% of Hib disease occurs among children 18 months of age or older, and 25% occurs above 24 months of age
So they're saying one in 1,000 kids under age 5 developed invasive Hib. Ok.

But then they multiply that by 5 to make it one in 200 kids by age 5.

Anybody see the problem there?

ETA:

You often hear "20,000 cases of Hib disease a year prevaccine!"

One in 1,000 in babies 0-12 months is 4,000 cases...times the first 5 years of life (coz that's how they get the "one in 200 by age 5" figure) is 20,000 cases a year.

That has to be where the "20,000 cases of hib disease a year prevaccine!" comes from.

mamakay's Avatar mamakay 05:35 AM 03-05-2009
I'm going to give you a clue with what's wrong with multiplying the "one in 1,000" by 5, to make it "one in 200", which give us the "20,000 cases a year" estimate:

http://www.cdc.gov/vaccines/pubs/pin...ds/hib-508.pdf

Quote:
Incidence is strikingly age-dependent. In the prevaccine era, up to 60% of invasive disease occurred before age 12 months, with a peak occurrence among children 6–11 months of age. Children 60 months of age and older account for less than 10% of invasive disease.
Look at the chart on page 119.

Whoever sees what's wrong with the 1985 math gets a cookie.
mamakay's Avatar mamakay 06:19 AM 03-05-2009
Another clue:

There are a few cases of invasive hib that still happened till age 10 and beyond. If they had multiplied the "one in 1000" till age 10 for a cumulative incidence, how many cases a year would be happening then according to that math? 40,000? Or, one in 100?

What if they took it to age 20?
Spectrolite's Avatar Spectrolite 06:45 AM 03-05-2009
:

...and wishing I could concentrate enough to actually do the math right now...
runes's Avatar runes 06:45 AM 03-05-2009
Quote:
Originally Posted by mamakay View Post
Another clue:

There are a few cases of invasive hib that still happened till age 10 and beyond. If they had multiplied the "one in 1000" till age 10 for a cumulative incidence, how many cases a year would be happening then according to that math? 40,000? Or, one in 100?

What if they took it to age 20?
Yes, if they do the math that way, then at some age, 100% (or, to be consistent with the terminology, 1 case in every 1 person ) will have contracted invasive HiB.

Does not compute.
runes's Avatar runes 07:04 AM 03-05-2009
Quote:
Originally Posted by mamakay View Post
I'm going to give you a clue with what's wrong with multiplying the "one in 1,000" by 5, to make it "one in 200", which give us the "20,000 cases a year" estimate:

http://www.cdc.gov/vaccines/pubs/pin...ds/hib-508.pdf



Look at the chart on page 119.

Whoever sees what's wrong with the 1985 math gets a cookie.
The first thing that jumps out at me is that they are citing those 1986 figures as pre-vaccine figures, but the HiB polysaccharide vaccine was licensed in 1985, so that's not technically pre-vaccine.

But let's just say, for argument's sake, that the chart is correct and it is reflective of the prevaccine numbers.

Quote:
In the early 1980s, it was estimated that about 20,000 cases occurred annually in the United States, primarily among children
younger than 5 years of age (40–50 cases per 100,000
population).
So they're talking about ALL HI infections, not JUST HiB. In the next paragraph, though, they say:

Quote:
From 1996 through 2000, an average of 1,247 invasive
H. influenzae infections per year were reported to CDC in
all age groups (range 1,162–1,398 per year). Of these, an
average of 272 (approximately 22%) per year were among
children younger than 5 years of age. Serotype was known
for 76% of the invasive cases in this age group.
Three-hundred forty-one (average of 68 cases per year) were
due to type b.
I had to read this paragraph several times to try to figure out what they are saying. It's so unclear. Out of the 1247 average cases per year, 272 were in kids 5 or younger. The serotype was known for 76% of this group but then they jump to say that 341 cases were due to type B. I have to assume that the 341 cases are talking about ALL cases, not in children under 5 because that is greater than 100% of all cases in children under 5, and that is a mathematical impossibility.


Clear as mud.
mamakay's Avatar mamakay 08:15 AM 03-05-2009
Quote:
Originally Posted by kidspiration View Post
Yes, if they do the math that way, then at some age, 100% (or, to be consistent with the terminology, 1 case in every 1 person ) will have contracted invasive HiB.

Does not compute.
YES!

Here is your prize.
http://thehealthblogger.com/wp-conte.../07/cookie.jpg

Most of the risk was clustered around age 6 months. Most cases happened in the first year of life. So they (probably closely to accurately) found that one in 1,000 kids under age 5 developed invasive Hib.
MOST of them were babies under one, some more under 2, and very few thereafter.
But they're just arbitrarily going to multiply the incidence by 5? That's going to render an extremely exaggerated figure.

Imagine if (this is an exaggerated fake scenario, to make the concept easier to understand) a fake disease we'll call "mamakay-type A" strikes 1,000 kids under 5 years old a year. 900 (90%) of them are tiny babes under 12 months old. The remaining 100 cases (10%) are dispursed among the 2-20 year olds. But a vast majority are happening in little babies under 1 year of age.

How many cases happen a year? (answer: a bit over 900. there are a few more cases coming in from older kids, too)

What happens if we want to pretend that the risk doesn't cluster around that one year? What if we assume the risk is equal for every year of the first 5 years of life, and just builds from there? Suddenly our 1,000 cases turns into an "estimated" FIVE THOUSAND (and beyond) cases.

But that's not true (in our hypothetical world, where mamakay-type-A is a killer). Really, every year is not the same risk-wise. Really, most of the risk happens in year one. So to take that risk and multiply it by 5 is to exaggerate the incidence almost 5-fold.

That's essentially what the CDC did to come up with the "20,000 cases", "one in 200" figure for Hib prevax.

They made a really basic mathematical error by multiplying the "under 5" incidence by 5.
ema-adama's Avatar ema-adama 08:20 AM 03-05-2009
Math is not really my thing, but I'll give it a go.

Quote:
Thus, in the United States, approximately one of every 1,000 children under 5 years of age develops systemic Hib disease each year, and a child's cumulative risk of developing systemic Hib disease at some time during the first 5 years of life is about one in 200. Attack rates peak between 6 months and 1 year of age and decline thereafter. Approximately 35%-40% of Hib disease occurs among children 18 months of age or older, and 25% occurs above 24 months of age
If they know that children are most at risk 6-12 months of age, and just multiply that number when they are most at risk by 5 to get to 5 years, it is not proportionate. I do not think I am expressing myself clearly, but it doesn't make sense to take the time period that you are most at risk and multiply that number by 5, when in each subsequent year the numbers would be less and not the same.

ETA: booooh, I missed the boat
mamakay's Avatar mamakay 08:40 AM 03-05-2009
Quote:
Originally Posted by ema-adama View Post
Math is not really my thing, but I'll give it a go.



If they know that children are most at risk 6-12 months of age, and just multiply that number when they are most at risk by 5 to get to 5 years, it is not proportionate. I do not think I am expressing myself clearly, but it doesn't make sense to take the time period that you are most at risk and multiply that number by 5, when in each subsequent year the numbers would be less and not the same.

ETA: booooh, I missed the boat
You get a cookie, too!

http://thehealthblogger.com/wp-conte.../07/cookie.jpg

Yes, multiplying the risk by 5 renders an exaggerated incidence. Most of the risk happened in year one. If you multiply the incidence by 5, you're going to triple or quadruple the number in a way that far exceeds reality.
ema-adama's Avatar ema-adama 08:44 AM 03-05-2009
Quote:
Originally Posted by mamakay View Post
Yes, multiplying the risk by 5 renders an exaggerated incidence. Most of the risk happened in year one. If you multiply the incidence by 5, you're going to triple or quadruple the number in a way that far exceeds reality.
That sounds much more eloquent
Marnica's Avatar Marnica 01:50 PM 03-05-2009
The CDC fudges numbers??? NOOOOOOOOOO that never happens.

They do it with all the other diseases why not HIB?

What I don't get from the numbers from the 1980's is that they are estimates right? I mean HIB was not a reportable disease until 1991 so how do they even come up with numbers that are relatively accurate for their estimates??
Marnica's Avatar Marnica 02:17 PM 03-05-2009
I had another thought about the numbers in general and the risk of contracting a VPD.

We are bombarded with all these numbers which instills fear most of the time. Lets say that the 1 in 200 number for HIB is accurate (which we know it;s not but for arguement sake).

If a child has no history of mental illness in the family then their risk of becoming Schizophrenic is about 1 in 100. One's risk of suffering form depression at some point in their life is about 1 in 20. Yet most folks don't sit around trembling in fear that their child will become schizophrenic or that someday they may be very depressed. Although if their was a vaccine for these things I wonders if people would run out and get it??
tmaue's Avatar tmaue 02:43 PM 03-05-2009
Quote:
Originally Posted by Marnica View Post
If a child has no history of mental illness in the family then their risk of becoming Schizophrenic is about 1 in 100. One's risk of suffering form depression at some point in their life is about 1 in 20. Yet most folks don't sit around trembling in fear that their child will become schizophrenic or that someday they may be very depressed. Although if their was a vaccine for these things I wonders if people would run out and get it??
Yes, and they would be added without delay to the schedule and parents would line there kids up to get them because to do otherwise would be irresponsible, right.
bri276's Avatar bri276 02:43 PM 03-05-2009
What confuses me about it is that every pediatrician I've talked to says they almost never see bacterial meningitis anymore. Pediatric journals and magazines reflect the same attitude, "Thank GOD for Hib (and Prevnar)"- moreso than for other vaccines. WHY do they say that if it's not true- brainwashing only goes so far, but it's so strange that all peds seem to have this idea that they constantly saw bacterial meningitis before the vaccine, and now they don't. And what about epiglottitis? That's gone, isn't it?
mamakay's Avatar mamakay 03:04 PM 03-05-2009
Quote:
Originally Posted by bri276 View Post
What confuses me about it is that every pediatrician I've talked to says they almost never see bacterial meningitis anymore. Pediatric journals and magazines reflect the same attitude, "Thank GOD for Hib (and Prevnar)"- moreso than for other vaccines. WHY do they say that if it's not true- brainwashing only goes so far, but it's so strange that all peds seem to have this idea that they constantly saw bacterial meningitis before the vaccine, and now they don't. And what about epiglottitis? That's gone, isn't it?
How old are they?

The ones I've talked to who say that were going through med school in the 80's and working in hospitals, vs now where they see a limited number of kids in a private practice.
k9sarchik's Avatar k9sarchik 03:08 PM 03-05-2009
My mom is an RN. She worked in pediatrics for a while in the 60's. She didn't even know about Hib. She said never was ever concerned about Hib when my sister and I were born.
Interesting how diseases are not a problem until Voila! we have a vaccine for it.
Scattershoot's Avatar Scattershoot 03:15 PM 03-05-2009
Quote:
So they're saying one in 1,000 kids under age 5 developed invasive Hib. Ok.

But then they multiply that by 5 to make it one in 200 kids by age 5.

Anybody see the problem there?
Ok, I'm just getting started, and I have not read all the posts yet. Thanks Mamakay for doing this. You break down numbers well.

So the first thing is the usage of cumulative numbers for the first 5 years of life (to make the odds seem pretty bleak), and at the same time admitting that after 12 months the odds of infection go way down.
mamakay's Avatar mamakay 03:20 PM 03-05-2009
Quote:
Originally Posted by Scattershoot View Post
Ok, I'm just getting started, and I have not read all the posts yet. Thanks Mamakay for doing this. You break down numbers well.

So the first thing is the usage of cumulative numbers for the first 5 years of life (to make the odds seem pretty bleak), and at the same time admitting that after 12 months the odds of infection go way down.
Yep.
It's just a very basic case of bad math.
bri276's Avatar bri276 03:23 PM 03-05-2009
Quote:
Originally Posted by mamakay View Post
How old are they?

The ones I've talked to who say that were going through med school in the 80's and working in hospitals, vs now where they see a limited number of kids in a private practice.
50's and over. My mom was in med school in the 80s when she had me and claims to have seen many cases during residency and in her early years of practicing. Her partners, around the same age, have said the same. Our pediatrician has also. I don't know how old the authors are in the mags and journals, but I've certainly read praise of the Hib vax several hundred times. Also reading the older reference books and textbooks, they definitely identified it as a not altogether uncommon occurrence, and they made epiglottitis sound pretty terrifying.
tmaue's Avatar tmaue 03:33 PM 03-05-2009
Wondering how antibiotic use plays into all of this. Could the use of antibiotics have caused changes in our bacteria and be a reason for a possible rise in Hi diseases? If Hi diseases were such a problem throughout time, why wouldn't a name have been given to them like with other diseases?
mamakay's Avatar mamakay 03:40 PM 03-05-2009
Quote:
Originally Posted by bri276 View Post
50's and over. My mom was in med school in the 80s when she had me and claims to have seen many cases during residency and in her early years of practicing. Her partners, around the same age, have said the same. Our pediatrician has also. I don't know how old the authors are in the mags and journals, but I've certainly read praise of the Hib vax several hundred times. Also reading the older reference books and textbooks, they definitely identified it as a not altogether uncommon occurrence, and they made epiglottitis sound pretty terrifying.
Right. During their residency they're working in hospitals, so yeah...they would have seen every case of invasive bacterial disease happening in the area. And in hospitals now, pediatric invasive bacterial disease is not exactly rare. It's just not all being caused by Hib.
k9sarchik's Avatar k9sarchik 03:44 PM 03-05-2009
Quote:
Wondering how antibiotic use plays into all of this. Could the use of antibiotics have caused changes in our bacteria and be a reason for a possible rise in Hi diseases? If Hi diseases were such a problem throughout time, why wouldn't a name have been given to them like with other diseases?
IMO, Hib was a non issue until it formula became popular. Since breastfeeding protects against Hib, formula fed infants are way more susceptible.
anewmama's Avatar anewmama 03:46 PM 03-05-2009
Can I just have a cookie? I need one. All this talk about disease, germs and Hi is making my head hurt.
tmaue's Avatar tmaue 03:47 PM 03-05-2009
Good point about the formula.
anewmama's Avatar anewmama 03:58 PM 03-05-2009
Ok, how about stepping away from the US and CDC. Let's start gathering data from other parts of the world. Particularly parts where some HIb surveillance had started but no HI vaccination program has been implemented. I found one study in Asia (some interesting points about race and HI disease)

http://publications.ksu.edu.sa/Confe...1/19991104.pdf
runes's Avatar runes 04:14 PM 03-05-2009
Quote:
Originally Posted by anewmama View Post
Can I just have a cookie? I need one. All this talk about disease, germs and Hi is making my head hurt.
Here you go, you can have some of mine. I already took a bite out of it.

Crunch, crunch, crunch.

mamakay's Avatar mamakay 04:27 PM 03-05-2009
Quote:
Originally Posted by anewmama View Post
Ok, how about stepping away from the US and CDC.
Compare and contrast:

From the HPA (the UK's CDC)

http://www.immunisation.nhs.uk/Vacci..._common_is_Hib

Quote:
Before the Hib vaccine was introduced, children under 4 were at most risk from Hib disease.

Over two-thirds of cases were found in children under 2, and the age group most at risk was babies of 10-11 months.

Around 1 in 600 children developed some form of the Hib disease by their fifth birthday
The US's CDC:

http://www.cdc.gov/vaccines/vac-gen/whatifstop.htm#hib

Quote:
Before the vaccine was developed, there were approximately 20,000 invasive Hib cases annually. Approximately two-thirds of the 20,000 cases were meningitis, and one-third were other life-threatening invasive Hib diseases such as bacteria in the blood, pneumonia, or inflammation of the epiglottis. About one of every 200 U.S. children under 5 years of age got an invasive Hib disease.
Did the HPA forget to multiply their incidence by 3-5 ?
anewmama's Avatar anewmama 05:06 PM 03-05-2009
So for for population of 100,000, UK is estimating that in 100,000 people, around 166 people will get HiB

And in the US, out of 100,000, around 500 will get it?


Is that how those figures play out per 100,000?

If so, that' an astounding increase in incidences for both countries compared to the study of Asia's incidences I posted above which puts the incidence of Hib somewhere around 40 in 100,000 for under 5 (Table 2). Not sure if my math is right but if it is... wow.

And on page 882 (pdf page 4) they say US rates are 4-5 cases per 100,000 for all age groups. So, do tell me my math is wrong...
Marnica's Avatar Marnica 05:23 PM 03-05-2009
Quote:
Originally Posted by bri276 View Post
50's and over. My mom was in med school in the 80s when she had me and claims to have seen many cases during residency and in her early years of practicing. Her partners, around the same age, have said the same. Our pediatrician has also. I don't know how old the authors are in the mags and journals, but I've certainly read praise of the Hib vax several hundred times. Also reading the older reference books and textbooks, they definitely identified it as a not altogether uncommon occurrence, and they made epiglottitis sound pretty terrifying.
There is no doubt the vaccine has been effective at wiping out invasive HIB disease so it makes sense that MD's would see fewer cases, but just because they saw a bunch of cases doesn't mean that it was very common. It just means there were MORE cases then than there are now. Its all relative
Spectrolite's Avatar Spectrolite 06:23 PM 03-05-2009
Some data from Finland:


http://www.pubmedcentral.nih.gov/art...i?artid=539842

Figure 1:
Cases of Hib meningitis in the Greater Helsinki area (current population >1 million), 1939-2003.




Am interested in finding out what the incidence ratio was prevaccine.
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