why vaccinated kids get those diseases

I was reading the threads in this section, mulling the whole vaccination thing again, and I came across quite a few people wondering, or commenting, on the fact that some of the kids that are vaccinated get the diseases they are vaccinated against.

In fact, the chances are that more kids that are vaccinated get those diseases than kids that are not vaccinated. So, being a mathsy-type of a person, I thought I'd have a go at explaining this effect to people who are curious.

It comes down to the fact that since most kids are vaccinated, most of the kids that get sick are vaccinated. However being vaccinated does actually protect a kid against that disease (not commenting here on other pros and cons of vaccinations - that isn't the purpose of this post at all).

Here's how it works:

Suppose there is a disease called thingyitus (yep, I made that up, because I don't want to get into a debate with anyone about whether specific numbers for specific diseases are wrong or right).

Suppose that vaccination for this disease has an 80% success rate (I think this is on the low side for most, not for things like the chickenpox vaccine, AIUI), by which I mean that 20% of the kids who are exposed to the disease, who are vaccinated, will catch it. Suppose that half of the kids who are exposed to the disease, who are not vaccinated, will catch it.

Suppose that 90% of kids in a school are vaccinated against thingyitus, and 10% aren't.

OK, if this disease goes around the school, and there are 100 kids in the school, what will happen is this:

90 kids are vaccinated, and 20% of them, or 18 kids, will catch thingyitus.

10 kids aren't vaccinated, and half of them, or 5 kids, will catch thingyitus.

So you can see that more of the kids who get sick are vaccinated than not.

It kinda looks like being vaccinated makes a kid more likely to get the disease. But that isn't the case at all.

5 out of 10, or 50% of the unvaccinated kids got sick.
18 out of 90, or only 20% of the vaccinated kids got sick.

Each unvaccinated kid had 2.5 times the risk of getting sick, compared to a vaccinated kid.

Now, I've chosen random and round numbers here. In practice I suspect that more than 90% of children are vaccinated for most things, depending on where you are. So the results would probably be more skewed than that.

The reason more vaccinated kids get sick than unvaccinated kids is simply because were are so many more vaccinated kids around.

So in this case, a total of 23 kids out of 100 got sick. The more unvaccinated kids you have, the more kids will get the disease. If half the kids were unvaccinated, there would have been 35 kids get it in total, (leaving out the details of herd immunity, which this calculation is too simple to include). If no kids were vaccinated, there would have been 50 kids get the disease, and if all kids were vaccinated there would have been 20 kids get the disease.

I hope that this explanation and example helps people understand this point better.

Tenar.

Thanks for that Tenar. I just want to add that the reason some kids still get the disease is that there immune system doesn't react as expected to the vaccine. The smallpox vaccine used dead cowpox cells. These cells were dead (harmless) and cowpox itself was not anything like as dangerous to people as smallpox. It was found that when you injected dead cowpox cells into someone their immune system forms antibodies against it. Then if the person is exposed to smallpox the body recognises it, because it's so similar to the cowpox, and it sends the antibodies it already made to deal with it. If the vaccine takes well the person will not contract the disease at all, if it takes but not very well, the person might contract the disease but will not become as ill as they might have, because although the antibodies they formed at vaccination don't offer complete protection, they give the body a head-start on fighting the disease.

This is why children who have had the chickenpox vaccine but still contract chickenpox often end up having a very mild episode with only a mild temp, a few days of being under the weather, and only a few blisters.

Certain people's immune systems do not respond as expected to vaccines and do not form the antibodies (that's why some vaccines use live cells of the disease which have been chemically or genetically disabled rather than dead cells or cells of a similar disease - to make the body more likely to react in the desired way). In the same way that some people's bodies don't react as expected to analgesia, some do not to vaccinations. There have been some studies in Africa that suggest that it is the absence of parasites in our systems which causes allergies and autoimmune problems. The evidence is still growing as there are not too many communities of adults who were fully vaccinated as children, but early results suggest that children who are fully vaccinated have a far lower chance of having excema, asthma, or food/environmental allergies if they have had repeated or prolonged exposure to roundworm, tapeworm or hookworm.

Bx

What about side effects of the vaccines due to what is contained in the vaccine? The kids who are not vaccinated - 0%.

Thanks Hoobley, I don't know much detail about the reasons why the vaccinations aren't 100% effective, but that makes perfect sense. I certainly didn't know that kids who are vaccinated have a lower risk of athsma etc, and would be interested to see a report of that research, as far as it goes.

Kelly, I was intentionally not getting into that stuff, just explaining the mathematical workings of this particular counter-intuitive thing. Of course any parent needs to weigh up the risk of the child having the disease against the risk of getting a side effect - that's the basis of the entire debate.

But then you don't add in those vaccinated children who will contract the illness, but yet not actually get sick, so they become a carrier of the illness and pass it on to those who are unvacinated - be it children or adults. The thought that vaccinated children can become disease carriers tends to worry me a little more than unvaccinated people.

Unvaccinated people can also be disease carriers a-la Typhoid Mary.

Oh of course, but as it stands it is assumed that once someone is vaccinated that they are *safe* kwim? You don't automatically look to the vaccinated people when there is a disease outbreak.

Kelly can you link me peer-reviewed, published (respectable journals please) medical articles showing which vaccines have side-effects associated with them, and the ingredients responsible please? Current vaccines? I have read the older stuff about ingredients no longer in use.

I would concur that by vaccinating DD i can only hope SHE is protected, though i haven't read of anyone dying because a vaccinated person gave them a disease they themselves weren't vaccinated against (again, links?). If vaccination only hopes to make the vaccinated person safe it is a shame so very many of the non-vaxers i know tell me their kids are safe because there's a high uptake and strong herd immunity where they live.

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The thought that vaccinated children can become disease carriers tends to worry me a little more than unvaccinated people.

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What difference does it make if you are unvaxed and sick how you got sick? Surely if you are unvaxed then the disease is a more of a voluntary possibility than if you are vaxed?

Bx

My concern with the non-immunised is exposure to someone from a foreign country who is not immunised (in a country with high rates of disease) and unknowingly ill that has traveled or migrated here and we have an outbreak because so many people have chosen not to immunise. It puts everyone at risk of contracting a horrible disease and could have catostrophic results.

I too would be interested in reading the documentation on the ill effects of immunisation for curiousities sake.

Those who ARE vaccinated are at significantly lower risk, whether they're exposed or not.

In Africa between 2002 and 2006 measles deaths fell by 91% due to the vaccination programme. Vaccination offers strong protection (not complete, but strong) against these diseases.

Bx

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My concern with the non-immunised is exposure to someone from a foreign country who is not immunised (in a country with high rates of disease) and unknowingly ill that has traveled or migrated here and we have an outbreak because so many people have chosen not to immunise. It puts everyone at risk of contracting a horrible disease and could have catostrophic results.

I too would be interested in reading the documentation on the ill effects of immunisation for curiousities sake.

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I think that in this scenario the disease that we will have to worry about isn't polio or another disease we can vaccinate for (although I do worry about polio) but something like bird flu. If/when bird flu or something similar becomes transmissable between humans we're probably in for a massive and horrendous epidemic.
I don't think there is anything much we can do to protect ourselves against the next big epidmemic.
TBH there's no reason to assume that it will travel from less developed countries to richer countries - the jump could occur anywhere.

I think that herd protection isn't as effective as some people believe because despite herd immunity measles is coming back in a big way. There is a strong correlation between the falling rates of immunisation and the increase of measles.
TBH if someone thinks that the risks from measles are so low that they don't mind their children getting the illness I have no problem with that. I had childhood illnesses because my mother wasn't big on vaccinating for the 'minor' diseases like chicken pox. They were the worst weeks of my life (and not just because I missed carnival with c-pox) but I did survive. On the other hand if they don't want thier children to get the illnesses but think that they'll be safe because other people have vaccinated, that strikes me as a tad selfish. Why should other children have to go though vaccination to protect their children?

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Those who ARE vaccinated are at significantly lower risk, whether they're exposed or not.

In Africa between 2002 and 2006 measles deaths fell by 91% due to the vaccination programme. Vaccination offers strong protection (not complete, but strong) against these diseases.

Bx

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It's great to see statistics like that. The death toll from disease in poorer communities is just heartbreaking. It's so easy to be complacent here and dismiss diseases like measles as uncomfortable and annoying and only rarely fatal that we forget in poorer communities they kill so much more easily.

Dach for herd immunity to protect the whole herd vaccine uptake needs to be at 95% and since Andrew Wakefields little injection into the issue it's fallen as low as 74% in some parts of the UK with the national average being around 82%. Local health authorities usually have the uptake stats available, but if it's under 95% your random unvaxed person is not safe.

I'm not sure if it's selfishness or a misunderstanding as to how vaccination and infection work, that makes some think they can "worry about it when it happens". DD was not vaxed against chickenpox because it's not offered. Does the varicella vaccine remove the risk of shingles? I have had pox and it was actually not too bad (i was only 6), but my whole family get shingles in old age and many of them suffer for several months a year... They're bringing the varicella vaccine in soon and i'd consider it for DD if it protected against shingles.

Bx

Bx, as far as I know locally, there have been some cases around here in the past few years of children getting c-pox even if vaccinated and the odd case of shingles in adults (some of which have also had c-pox). Don't get me wrong, I"m not against vaccination by what I've said - heck I have 3 vaccinated children and a baby who was vacced till 6mths, I am choosing not to vaccinate any further for any of them. You just can't assume that even vaxed people are safe or wont become carriers is all my issue was in relation to the OP's 'theory' so I don't have links, just my mind thinking overtime ;). I won't be relying on herd immunity either because I think that's a pretty poor and lazy way to choose not to vacinate.

And since the chicken pox vaccine has been brought into the discussion, I have come full circle on that one. I was a staunch supporter of it and had my older three vaccinated for it even though it wasn't on the schedule for them, but in light of my own research I don't think it gives a strong enough protection for long enough.

Um side question - can diseases truly die out?

That's why it's not been offered in the UK so far Trillian, the NHS cannot AFFORD to blanket-vaccinate with an ineffective vaccine, and i think the varicella vaccine efficacy is the lowest at around 80%, though as i said, of the 20% who aren't immune after vaccination, they do seem (anecdotally to me, because i've not looked for any studies) to get less severe attacks. Unlike Dach i didn't find the pox too bad and certainly not bad enough to go out of my way to vax for (she'd have to be offered catch-up as it wasn't on her schedule), but if the 80% who don't get chickenpox after vaccination ALSO can't get shingles, it really *might* be worth it for DD.

Bx

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Um side question - can diseases truly die out?

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To this day, smallpox is the only human infectious disease to have been completely eradicated. Apart from the samples of it that they have stored in 2 sites in the USA & Russia..... biological warfare anyone?

Lulu, yes. Like any living thing, they can become extinct. Smallpox is extinct in the living population, though it exists as a bilogical weapon (allegedly, though it's almost certainly true).

When you get measles, while you have the disease it is multiplying like crazy in you and getting out via liquid droplets (in sneezes, coughs and your breath) to other people. If they inhale it and are not immune (through vaccination or previous exposure) they get infected. However, your body launches an attack on the measles cells and kills them all, and you get better. If enough people are vaccinated that there is no-one for your measles to infect then it dies out.

Polio is on the verge of eradication right now, which is tremendously fantastic news.

Bx

Diseases can die out like any other living thing.
One example is a disease called The Sweats that killed large numbers every summer in Medieval Europe. Now its disappeared.
Of course it might exist in tiny pocket rather than being totally extinct just as some animal and plant populations do.
Of course human agency makes them more likely to die out - same as other life forms.