Homeopaths in denial

This is a tidy-up of a comment I posted on homeopath Steve Scrutton’s blog.


Steve, you don’t seem to understand what a denial means.

Imagine somebody (a he in this case) who anecdotally helps people by playing the piano. This goes on for years. People listen to the music and often feel better – either then or a little while later. Every now and again somebody with a serious illness will get better – breast cancer say (relatively high remission rate) – and he makes sure the world knows about cases like that (selection bias).

Then a scientist does a well designed study of the piano playing and the results are ‘no better than placebo’. The pianist rejects it – its just one study and he rationalises it away.

Over the years hundreds of studies are done – and an interesting phenomenon emerges. The efficacy of the piano playing treatment correlates inversely to the quality of the studies, with the best studies concluding ‘no better than placebo’ – meta analysis and review back this up.

The pianist still refuses to accept this now good minimally-subjective evidence – arguing perhaps that his treatment is unsuitable for formal study because it’s all very personal – and maybe starts cherry-picking some of the more positive but poor studies.

He is now in denial.

Good minimally subjective-evidence says one thing, but because of his bias (and business) he is rejecting it. He resolves the dissonance with rationalisations (e.g. unsuitable for study) and carries on.

This is exactly where homeopathy is. Forget the ‘it cannot work’ arguments – they are irrelevant. It does not work (more than placebo) as shown by the good evidence. Homeopaths are in denial. Looking for plausibility and mechanism in the face of such evidence is farcical.

Interestingly there is some evidence that overt placebo works. Homeopaths could perhaps go down that route and only ‘treat’ self limiting or cyclic chronic illness. – i.e. be intellectually honest, recognise the denial, embrace the good evidence and say – OK, homeopathy is placebo but overt ritual placebo can still help in some safe contexts. And there are probably other ways to strategise.

Contrary to your claim, the skeptics are not in denial. They are just following the best evidence because of a well placed confidence in the scientific process (over time). Essentially a skeptic (and me) wants to know how the universe works – they don’t particularly care what actually emerges. They may have a casual preference in one thing or another, but they will never let that compromise ‘the truth’.

If the evidence had shown that homeopathy worked then the skeptics would have embraced it. But it doesn’t and that’s why they are angry. Angry at homeopaths using homeopathy in contexts where it is inappropriate and potentially dangerous – like cancer and vaccination. People have died because of the inappropriate use of homeopathy.

Denial means rejecting a contextually reasonable volume of good quality evidence while embracing ones ideology and bias. Denial creates cognitive dissonance which is then resolved by comforting rationalisations.

Other examples are 9/11 truthers, holocaust deniers, climate skeptics (confusing label), creationists and vaccine freeloaders (anti-vaxxers that do not vaccinate simply out of choice).

Should pro-vaccine parents engage in the vaccination debate?

Originally a guest post in Vaccines Today.

Should pro-vaccination parents engage and debate with anti-vaccination parents who are posting misinformation in online discussion groups?

Vaccines are not 100% effective, some people cannot be vaccinated for health reasons and some vaccines cannot be given before a certain age. These facts mean that our vaccine decisions can and do affect other people, so there is a social element to vaccination. By not vaccinating ourselves, we could be endangering the life of a child too young to receive the pertussis vaccine for example.

As a collaborative social enterprise, there are further benefits. If enough people are vaccinated against certain diseases, herd immunity will emerge, providing a space for those who cannot be vaccinated for age or health reasons to be indirectly protected. And for some diseases, achieving and maintaining herd immunity can lead to its elimination and possibly eradication. Measles for example could be eradicated like this.

But there are risks associated with vaccination. While most of the adverse effects of vaccines are mild and transitory, there is a real, but tiny risk of more serious and long lasting reactions. We are also vaccinating against a backdrop of morbidity which means that temporal correlations of post-vaccination illness will inevitably happen and we are very good at noticing such things.

The possibility of a severe adverse reaction can be a stumbling block for some parents. Others don’t vaccinate because of anecdotes of illness following vaccination. And there are lots of other reasons, like becoming scared of vaccine ingredients and a general mistrust of science in general. But they all have one thing in common – they are based on simple logical fallacies, which allows us to answer the question of the title.

Because our vaccination decisions affect society and because by collaboratively embracing vaccination, other societal benefits emerge like herd immunity and disease elimination, we should engage with anti-vaccination parents. Because the reasons for not vaccinating are usually based on simple logical fallacies, it means we can engage as parents; we don’t need the detailed knowledge of professional health workers.

By getting involved with the countless anti-vaccination discussion groups and simply pointing out their logical errors, we may be able to partly neutralise the vast quantity of vaccine misinformation out there and reduce the number of people who choose to not vaccinate after “doing their research” on the internet. It is true that some sites will ban you after a few polite posts, but if enough parents engage in debate, this behaviour will become apparent and act as a ‘tell’ in its own right.

Vaccination is not 100% effective

It is not uncommon to see online discussions with arguments of the form if your child is vaccinated, what risk is there from my unvaccinated child?.

The fact is that while vaccines are generally very good, they are not 100% effective in terms of seroconversion rates. Some vaccinated individuals can still catch and transmit the diseases they have been vaccinated against; although often the symptoms are usually less severe than in the unvaccinated case.

Ideally vaccines should be effective enough to reach the requirements needed for herd immunity. Herd immunity is a wonderful phenomenon whereby some individuals can escape both the risk of infection and the risk of vaccination (vaccination does carry small risks). It can be shown for example that assuming an ideal 100% effective vaccine, we need to vaccinate about 94% of children to eliminate measles. This 6% ‘breathing space’ is fortuitous because there are a number of people who cannot be vaccinated because they are too young or their immune system is compromised in some way.

When people deliberately don’t vaccinate their children for no other reason than personal choice, they are using up some of this precious 6%. Their children will generally be safe because they are being protected by the herd (freeloading), but at some point the space will be used up and herd immunity will break down. By implication, vaccination is not simply be a matter of personal choice because your choices affect your neighbours; it’s far more of a social collaboration.

Imagine a measles vaccine that is 99% effective after the scheduled number of doses. By implication we need to vaccinate more than 94% of children to maintain herd immunity and it follows that if the measles vaccine is less than 94% effective, herd immunity cannot be achieved because we have to theoretically vaccinate at a rate of over 100%. This is why we try to vaccinate all children, to create as much space as possible using herd immunity for those that really need it and to counter the less than perfect effectiveness of vaccines.

Even if a vaccine is not effective enough to achieve herd immunity it can still be highly desirable. Most diseases go though epidemic cycles. By vaccinating, both the magnitude and frequency of the epidemics are reduced. A side effect is that the average age of infection increases and for some vaccines this may outweigh the benefits because some diseases are worse when contracted later in life. Pertussis is an example of a disease that cannot presently be eliminated by childhood vaccination alone because of the efficacy of the current vaccines, but is still desirable because it massively reduces epidemic magnitude and frequency, and is less severe when caught later in life.

Which button would you click?

One thing antivaxers have going for them over a science based argument, is playing the emotive card. Consider this from a debate I was involved in tonight:-

That anyone can say it’s ok to sacrifice a few children for the “good” of others (even though it’s ridiculously untrue) is beyond insane! How would you feel if YOUR child was one of those vaccine injured children….would it still be ok then? Are you seriously saying you’re happy for your child to die so others can live?

Consider two buttons. The first kills 1 in a 1000 children of some population at random and the second kills 1 in 1000000 children of the same population at random. Which one would you click? Yes, it’s a no-brainer. Yet this is exactly the sort of choice we have to make with respect to vaccination strategies – and some antivaxers would have us click the first button – the “don’t vaccinate” button.

Neither button is desirable, but we have to click one of them and the clear winner is button two. Because serious adverse reactions to vaccination are so rare, they often have public exposure (and rightly so), making them an easy and compelling target for antivaxers.

It’s easy for the antivaxer to say things like – “what are you going to tell those parents?”, but exactly the same can be asked if we stopped vaccinating – “what are we going to tell the parents of the orders of magnitude more children that will now die from a vaccine preventable disease?”. Can you imagine their response to – “we stopped vaccinating because there were some very rare but serious adverse reactions…”.

Everybody knows that vaccines carry an inherent risk, but we are all in this together. We can stop vaccinating and watch tens of thousands of children die, or join together and fight a common enemy. Measles for example could be eradicated if we could get over our generally misplaced fear of vaccines.

So much passion is wasted on arguing against vaccines in general, when in fact it could be refocused on lobbying to: improve research into developing new vaccine technology – for example to replace the live vaccines, phase out multi-dose vials, improve vaccine efficacy and improve screening technology – the latter indirectly helping to counter the human tendency to associate illness following vaccination as an adverse reaction.

Consider what John Salamone achieved.

In such a world those who still cannot be vaccinated for age or health reasons really can be identified and successfully cocooned in the herd because everybody else is vaccinating – and there is a very real chance of eliminating and eventually eradicating some of these diseases – a manifestation of emergence from a collection of achievable goals.

There again many people I ask really do want to click button one – they say it online – in public. How would they strategise? Diet is favourite, followed by vitamin supplements!

The target of this post are antivaxers who for no reason other than personal choice (not medical/age reasons) decide not to vaccinate.

Edit: Some cowardly Anon has written a response to this on Meryl Dorey’s blog.

Vaccination is a social responsibility

What a wonderful thing it is to be able to vaccinate our children, not just to protect them, but those around them that are too young to be completely vaccinated or cannot be vaccinated for health reasons. What a wonderful gift herd immunity is to and from humanity. Yes there are risks of adverse reactions to vaccination but such risks are microscopic and completely outweighed by the benefits.

While vaccines do a great job of protecting an individual, they are not a hundred percent effective and contrary to intuition, in some contexts, it is safer to be unvaccinated in a highly vaccinated population, than be vaccinated in a highly unvaccinated population – we all rely on herd immunity – not just those that cannot be vaccinated. The less effective a vaccine is, the more we all rely on herd immunity.

What an incredibly selfish thing it is then, to not vaccinate (unless you cannot for heath/age reasons) – to rely on your neighbours to protect your children rather than take a microscopic risk – to disengage from the wonderful social collaboration from which herd immunity emerges. Imagine what would happen if we were all that selfish.

Given that vaccination not only helps the individual, but the local population, it is especially sad that these same people blindly engage their children in activities that are orders of magnitude more dangerous – like driving them to school.

We all have bias and it’s so easy to resolve it with ‘intuition’, ideology and anecdote – but a truly caring and thoughtful person will live with any dissonance and act for the sake of their children and their neighbours, rather than indulge in the escape of their own cognitive comfort.

If you are a vaccine skeptic, think about this for a moment – you are only getting the choice to not vaccinate and have your children grow up without the probability of serious illness because most people around you have fulfilled their social responsibility and had their children vaccinated. Our children will be protecting your unvaccinated children. You are relying on your neighbours to be vaccinated. But the more people decide to not vaccinate, the more disease will drift back until at some point thousands of children will be dying again every year. Herd immunity builds up a resource – a precious space where a limited number of people can be protected in the herd – don’t contribute to a tragedy of the commons and deplete something so essential to the very young and those that cannot be vaccinated.

Be a thoughtful caring loving rational human being – vaccinate your children – get your boosters – it’s not just a personal choice like hairstyle is.

“It’s not just a decision you make for yourself, it’s also a decision you make for your neighbour.” Paul Offit.

“If you choose not to vaccinate, and you then contribute to a decline in herd immunity, you’re putting other people at risk… People need to be honest with themselves about what the consequences of their actions are.” Seth Mnookin.

Antivax maths

for 100 > x > 0 : 100 – x = 0

for V >> U & Iu >> Iv : VIv < UIu

if p(x) > 0 : p(x) = 1

if p(x) < 1 : p(x) = 0

“The outbreak was in the vaccinated”

It is often argued that because the number of infections is greater in the vaccinated fraction of a population, compared to the unvaccinated fraction, the corresponding vaccine is not effective.

But this is a simple logical error.

The point being that while the number of infections in the vaccinated can be greater, because of a high vaccinate rate, the percentage will be lower unless the vaccine really is ineffective.

Another way to think about it, is to consider that a small percentage of a large fraction of a population can easily be greater than a large percentage of a small fraction of a population.

This little Javascript app let’s you experiment with the numbers and set up your own scenarios, with a custom link.



Imagine a school with a 1000 pupils and a 95% vaccination rate, so 950 children are vaccinated and 50 are not vaccinated. A highly infectious disease is brought to the school by a visitor that infects say 40 of the 50 unvaccinated children. No vaccine has a 100% seroconversion rate and for the purposes of illustration let’s say that 80 of the 950 vaccinated children become infected.

There are twice as many infected vaccinated children as infected unvaccinated children. Does this mean that vaccination doesn’t work? No, of course not, if vaccination didn’t work, there would be around 760 infected vaccinated children.

A much better and intellectually honest way to compare the groups is to use the fraction or percentage that become infected. 80% of the unvaccinated children are infected, while only 8.4% of the vaccinated children are.

Thus in this context vaccination reduces infection by (1 – 8.4/80), i.e. by almost 90%. This could be considered to be the contextual or point vaccine effectiveness. A confidence interval for this value could be calculated if required to make sure the scenario is statistically sound.