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Herd Immunity

(289 Posts)
Tabitha8 Sun 09-Sep-12 16:42:12

A simple title for what I think is probably a complex subject.

If we have herd immunity to an illness as a result of vaccinating our children, how is that maintained given that we don't vaccinate ourselves, the grandparents, our neighbours, etc?

MordionAgenos Wed 12-Sep-12 11:27:23

@Tabitha believe me if you had met anyone who had polio as a child then they would know about it (and so would you). But there's a reason why you don't meet many of them. Most of them died and many of those that didn't die while they had it died not long afterwards. The prognosis for life in an iron lung (which was where many of the survivors ended up) wasn't long.

sashh Wed 12-Sep-12 11:41:36

Tabitha

That's intersting. OK try 'would you have (let your children have) holiday vaccinations.

bumbleymummy Wed 12-Sep-12 12:17:32

LeBFG, as I've previously pointed out, no one is demanding that we all expose ourselves to whooping cough to gain natural immunity and protect the 'herd'. If you accept that natural immunity can also wane (although in general it lasts longer, as you are well aware) then I'm not really sure how you can put forward a convincing argument for creating herd immunity with the vaccine knowing that it is even less effective.

BBB, polio isn't always serious. 95% of people will have no or mild, flu like symptoms and may not realise they have polio. Around 1% may have paralytic polio but the effects aren't always permanent. Obviously the paralytic form can be very serious and I'm not belittling that. I just wanted to point out that isn't 'always a serious illness'.

I realise it is asymptomatic is 90-95% of people but then there are a lot of illnesses that we carry that we don't know about so I wouldn't really count them as having had the disease even though I suppose medically we have. It is still serious in those who get it - I don't call 'flu-like symptoms particularly mild. Flu makes you feel like crap so I am told - I don't know for sure as I am fortunate never to have had it. I have had some terrible colds but never flu.

Of the people who get symptoms a good proportion of those do get the more serious sypmtoms too - apparently 20-40%. That is a lot when you compare it to the percentage that get complications in other diseases like chickenpox.

seeker Wed 12-Sep-12 13:06:24

Bumblymummy-this is a serious question. Would you be happy for your child to go unvaccinated into an area where there were active polio cases?

bumbleymummy Wed 12-Sep-12 13:26:22

BBB, it is possible to have mild flu. The mild flu like symptoms they mention are headache, tiredness etc. I'm by no means trying to say it is in the same league as CP but saying 'it is always serious' or 'most of them died' isn't quite accurate.

Well, they wouldn't have much reason to go to those areas and tbh if they did I would be more worried about things other than polio!

seeker Wed 12-Sep-12 13:32:44

Really? So your child, for example, decides to do DfoE or something similar in areas where polio is endemic and you wouldn't worry about it?

LeBFG Wed 12-Sep-12 13:55:35

The vaccine maybe less effective bm but there are at least three things you are overlooking.

One, herd immunity increases with increased number of immune people. Wrt wc, herd immunity effect is clearly in operation as "Mortality and morbidity have fallen drastically in parts of the world where toddlers have been systematically protected with efficacious whole-cell vaccines"

Two, when people are vaccinated, they are not required to become ill in order to create herd immunity.

Three, both naturally-aquired and vaccination immunity durations are highly variable, in some people lasting as little as 4-7 years and in others up to 12-20 years.

These factors (and others, such as severity after re-infection with wc) mean the case is not as simple as you make out bm.

BM - We are quibbling over what serious means. Mild flu isn't really flu in my book. It wouldn't register as such anyway. Nowhere have I read that those with symptoms that are like 'mild flu', just plain old fashioned flu, headache temperature, sore throat, gastric problems etc, and therefore not very nice.

I'll assume that you aren't attributing the 'most of them died' comment to me as well since I haven't said that. It isn't true!

Your children may make the decision to go to the places where polio is endemic long after you have control over where they go. Will you tell them why they are unprotected. Perhaps they will join the armed forces and have to go to places that people from this part of the world probably wouldn't venture. Or just hope that because the vast majority of us have had our children vaccinated yours don't need to bother because the disease has been wiped out.

LeBFG Wed 12-Sep-12 13:57:27

No point asking questions like that to bm, seeker. Bm would be happy to live in modern world without vaccines. Isn't that right bm.

bumbleymummy Wed 12-Sep-12 14:52:20

Are you saying that we have herd immunity to whooping cough at the moment LeBFG? Perhaps you should clarify what you mean by herd immunity (see above). I'm not sure why you have used your quote as an illustration of herd immunity. Wouldn't you just attribute that to the vaccine offering some protection to the child itself? I'm not overlooking those things btw. I'm not sure why you think I am.

Seeker(and BBB) at that age it would be up to them anyway but, as I've already said, I would have bigger worries!

BBB, I'm not saying they're nice but obviously those symptoms can be mild or more severe. There is a scale. No, I wasn't attributing the 'most of them died' comment to you - just pointing it out as incorrect.

BFG, I see you're still twisting things said on a previous thread. Let's just say I probably wouldn't be panicking about it as much as some of you would smile

seeker Wed 12-Sep-12 14:59:42

"Seeker(and BBB) at that age it would be up to them anyway but, as I've already said, I would have bigger worries!"

I do find it fascinating that people who are opposed to vaccination will never answer a straight question like this. I've asked it frequently, both on here and in real life, and I have never had an answer.

bumbleymummy Wed 12-Sep-12 15:01:40

I've answered you twice now confused. Maybe you just aren't getting the answer you want.

seeker Wed 12-Sep-12 15:09:14

No you haven't. You've said it would be their choice and you would have other things to worry about.

You haven't said whether you would be happy for your unvaccinated child to go into an area where polio was endemic- as it was in this country until the early 60s.

LeBFG Wed 12-Sep-12 15:15:14

Herd immunity, as it is correctly used and widely understood in the literature is NOT herd immunity threshold. I would highly recommend you read the wiki definition if you have problems understanding this.

Some sort of herd immunity to wc exists because babies too young to be vaccinated are dying less and are ill less than in the pre-vaccination era. This is indisputable (except by Prof bm perhaps). That there is now a growing incidence of wc more recently is another issue. Wc herd immunity exists despite the fact the vaccine in less than perfect.

bumbleymummy Wed 12-Sep-12 16:13:20

I posted quotes and links earlier about the various definitions of herd immunity including a link to a study that used it in the context of herd immunity threshold. Perhaps you should refer them all to wiki?

In any case, most literature will tell you that a significant proportion of the population need to be immune for there to be any herd effect. Why do you think the growing incidence of WC is a separate issue?

bumbleymummy Wed 12-Sep-12 16:18:49

You might have to refer these people to wiki too.

seeker Wed 12-Sep-12 16:23:08

Why are we debating the meaning if 'herd immunity"? Surely we all know what it means for the purposes of general discussion?

Still no answer, bumblymummy?

bumbleymummy Wed 12-Sep-12 16:38:08

Doesn't it make sense to clarify what we are talking about for the purposes of the discussion?

I've already answered you seeker. I wouldn't be happy for them to go there but it wouldn't be polio that would be worrying me. If there was an outbreak of polio here, in the UK, would I be worried - no.

MordionAgenos Wed 12-Sep-12 16:52:59

@bumbly The 'most of them died' comment was made by me and was correct but I didn't make it clear I was referring to the respiratory type of polio (which is the type my DH had). That's the type that put people in iron lungs. That is the really scary type (weird to think that the type of polio that could result in being in callipers all your life, as happened to two by then adults I knew when I was a kid, was actually the 'good' type of polio).

The number of people who have a memory of the last great UK epidemic is diminishing all the time. The number of people who had first hand involvement is even smaller. The number of people with relatives who were involved is obviously greater but still - it's very unusual, especially in certain parts of the country (less so in London, or some of the other worst hit centres in the late 50s I suppose). DH is the only person our family GP (who is older than me but who doesn't come from London) has ever known who had polio.

MordionAgenos Wed 12-Sep-12 16:53:58

The reason I'm going on about this is because some posters are being ridiculously ludicrously dismissive of polio and its possible impact.

LeBFG Wed 12-Sep-12 16:56:16

Your last link in no way contradicts what I just said: more people immune, greater the herd immunity. Pretty obvious really. To ask your question back: do you think we have herd immunity to wc?

You may (or may not) be interested to know that there is research into the effect of lower transmission rates leading to more virulent wc presentations. This is not to do with herd immunity but simply that more people are immune now due to vaccinations so transmission of the disease has lowered.

LeBFG Wed 12-Sep-12 17:03:46

Oh, some paper may define a parameter x and call it herd immunity somewhat inaccurately btw for ease of reading. Or refer to the threshold effect as simply herd immunity. That was why I said 'as it is correctly used and widely understood". The wiki definition is highly uncontroversial. For ease of understanding, the wiki definition should be used imo when talking about herd immunity. The herd immunity threshold has a very specific meaning and is another thing.

seeker Wed 12-Sep-12 17:27:28

"I've already answered you seeker. I wouldn't be happy for them to go there but it wouldn't be polio that would be worrying me. If there was an outbreak of polio here, in the UK, would I be worried - no."

Could you explain why? Assuming the outbreak was local to you?

AnitaBlake Wed 12-Sep-12 18:03:32

Sorry, just got back to this. No-one is quite sure why the wc epidemic is happening now. I wonder if it had anything to do with the wc vacc scare in the 70's and 80's when vacc rates fell to 30%. Those babies are parents now. Even last year most cases of wc were in unvacc'd kids (at least the ones I heard of at work were).

I must also apologise about the wc death rate I quoted. After speaking with the vacc specialist at work today, nine babies have died this year in this country due to wc. There are intentions to start vaccing pg women to try help reduce the incidence in babies.

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