 Do you have any thoughts about what drives people who don't want to vaccinate their children? Well one very simple consideration is that if we don't have any polio in this country and we don't in Australia, we haven't had polio in this country for many years, then why should my child have a vaccine to protect them against a disease which doesn't exist in this country? After all, the vaccine has a very slight risk associated with it and there is no risk of the disease. What people of course forget is that their children, when they grow up, are likely to go off to parts of the world where the infection still does exist and it's a bit late to get the vaccine after you've already got the infection. So that's one reason, it's not really a problem anymore. In the old days people used to rush to get vaccines. The polio vaccine was fought for when it first became available in the 1950s in the United States because there was an epidemic of polio every second year and people died and people became paralysed and everybody knew what polio was. But now the next generation of mothers and fathers don't actually see polio anymore so they don't see a risk. There's a second group that say okay well if everybody else is vaccinated I don't need to get my kid vaccinated and of course that's quite correct because if there's no way of the infection spreading for example if everybody's vaccinated against measles except me I'm fine. But what they forget is that if only 99 out of every 100 people are vaccinated against measles that's still enough to allow an epidemic to occur because every one person that gets infected will infect potentially 100 others and if 99 are protected they won't get it but the other one will and will pass the infection on so all the people who are not immunized will be at risk. So that's a second reason which is not a particularly good one but you can understand why people think that especially for infections which are not as infectious as measles. Measles is incredibly infectious but most infections are not that infectious. The third reason why people think that is that they've listened to somebody who's had supposedly an adverse reaction to a vaccine. They're persuaded by their neighbour saying when my little kid got it then he had convulsions afterwards. Now that's a rare complication of measles vaccine for example. Quite often the febrile convulsions turn out to be occurring with or without the vaccine but the story gets around and Mrs Smith's daughter got into real trouble after vaccination and wouldn't it be better just not to be vaccinated. Those people are persuaded very rapidly when an epidemic of the infection occurs for example with the whooping coffin epidemics we've had recently that their kid really ought to be vaccinated but it takes the infection to do it. And then there's a small group of people who basically just have a set of disbeliefs about how the world works and they don't believe in the infectious nature of disease for example they have an animistic approach to how people get disease it's punishment from God or it's against my religion or whatever. And they just have these fixed beliefs and by and large they stay fixed. You've mentioned that one of the reasons that people tend not to immunise their children is like you said there isn't polio in the country but if there was it would obviously people would be flocking to be vaccinated. Can you paint a picture as to what some of these things look like polio and measles and so on for people who aren't in cloud? Yeah measles in most people's mind dismissed as just a spotty skin disease and for many people who get measles that's all it is but one in a thousand will get a serious internal complication and one in a hundred thousand will be left with major brain damages as a result of measles infection so that measles if you got the unlucky one is not a trivial disease and in fact more people die worldwide of measles than of any other infection apart from diarrheal disease. It's quite a significant problem particularly for young kids indeed that's why we push to get kids vaccinated as early as possible in the developing world because the risk of measles killing you is greatest when you're between the ages of zero and two. Polio well for 99 people out of 100 polio is a diarrheal illness which goes away after a couple of days but for one in a hundred people it leads to paralysis maybe of a leg or an arm. If you're really unlucky it paralyzes your vocal muscles and of course the paralysis is permanent because the nerves that work these muscles are destroyed by the virus so that's why people used to end up on respirators for the whole of their lives because they were basically left unable to breathe for themselves. Another vaccine that I've been involved with of course is the vaccine for cervical cancer and again the virus that causes the cancer for 98 people out of 100 it's a trivial infection they never know they've had it but for the 2% of people that get persisting infection they can go on and get a cancer which will kill them and if it's not detected early enough it's a lethal infection in fact papillomavirus kills more people worldwide quarter of a million people worldwide die every year as a result of papillomavirus infection so that's a very significant burden it's the ninth commonest cause of infectious disease death. One of the issues that we're dealing with in the course is the idea of cancer clusters so these are quite common we even had a case I think in 2006 in Brisbane if you had much experience do you know the phenomenon or why they tend to pop up? When I sat on the international agency for cancer research a scientific advisory board for a few years this was one of the topics that used to come up regularly it related to use of mobile phones it related to stuff being discharged from factories some cancer clusters are very real environmental pollutants can produce a cancer cluster and sometimes those cancer clusters are the first evidence of the particular chemical that can cause a cancer many matter of disease for example is an example where toxic pollution produced a whole swathe of cancers and then the Bhopal disaster as well where there was a release of methyl cyanide I think it was into the environment and that produced a whole cluster of cancers but most of the clusters that people are worried about that mobile phone tower this particular power station there are half a dozen cancers or ten cancers in the community and somebody says that's a cluster what they forget is that rare events occur rarely but they do occur and if you've got a population of 7 billion and you're sensitized to looking for clusters you'll find them and you'll find them with just the probability that you would expect if it's all random in other words a statistical analysis plus a close look to see if it really is a cluster because quite commonly what you find is they say well we've got six cancers but it turns out that they're all quite different and they're not really a cluster of anything they're just six people who were unfortunate to get a disease so that it's partly statistics and partly common sense but you just have to remember that people do get struck by lightning every now and then and cancer clusters are in the sort of struck by lightning or one in a million chance but it does happen The title of the course is the science of everyday thinking given your career, given your experience in vaccination and immunology and so on what advice do you have for the students, the 60,000, 80,000 students who are taking the course to improve their everyday thinking? I think that basically the more educated people are the more likely they are to make correct decisions about things you can never have too much education even if you're not going to be a scientist if you're not going to go out there and do experiments understanding the scientific process the fact that you can make a hypothesis or call it a guess if you like and then test it and then at the end of the testing we're reasonably confident about whether your guess was correct or not that is the basis for making decisions about things and that's the message that I would always leave people with so that even if they don't do the experiments they should be aware that when data are gathered through experimentation it is actually testing an idea and it can be falsified you can get an answer that says your hypothesis was wrong the alternative is straight guesswork you know, don't bother doing the experiment let's just say I'm right and then you get an answer and that's not an uncommon approach to things but it does lead to some very interesting mistakes so I think that the important thing is to say that wherever possible test the hypothesis My name is Ian I think about infections