” The motivator, in terms of getting vaccinated, is perception of personal risk. ” -Dr. Fisman
Dr. Fisman is an Associate Professor of Infectious Disease Epidemiology at the Dalla Lana School of Public Health and Health Policy, Management and Evaluation at the University of Toronto. He received his MD degree from the University of Western Ontario, and an MPH from Harvard School of Public Health; he also completed fellowships in clinical infectious diseases and health policy within the Harvard system. From 2005-2006 he served as a Visiting Scholar and Visiting Assistant professor at the Center for Health and Wellbeing at Princeton University. Dr. Fisman’s research interests involve application of novel epidemiologic methods to the study of infectious diseases of public health importance, including vaccine-preventable diseases, sexually transmitted infections, and bacterial respiratory pathogens. He is currently a member of the CIHR-supported Canadian Pandemic Influenza Modeling Network (CanPan), and has received grants from the U.S. National Institute of Allergy and Infectious Diseases on seasonality of infectious diseases, and from the Ontario Ministry of Innovation’s Early Researcher Awards program, and he was a recipient of the GSK Elion Young Investigator Award for his work on the mathematical modeling of herpesvirus infections.
— excerpt from The Canadian Association of Veterinary Epidemiology and Preventive Medicine (CAVEPM) 2010 Conference Plenary Speakers Bio: http://www.ovc.uoguelph.ca/cavepm/page/speakers.cfm
Transcribed interview- Vaccination | April 06, 2011
for the full article: https://karenquinto.com/2011/05/31/holes-in-the-herd/
Dr. David Fisman: Hi there, how are you?
Karen: I’m good how are you?
Dr: I’m good thank you.
K: Great! You’re going to Montreal?
Dr: Yeah, I’m going to an infectious disease meeting for the next couple of days.
K: Oooh, exciting.
Dr: Yeah, for sure.
K: I wanted to write about people’s perception and misconceptions about the vaccine and what motivates people to take shots, and what motivates people not to take shots. And I was speaking to two girls today, they’re second year here at biomedical engineering. It was interesting because one of them is Canadian born and since she doesn’t get the flu often therefore she doesn’t really need the shot. The other was born in India and she feels that she has stronger immunity from living in another country. What do you think about those responses?
Dr: Well, you’ve got an end of two experiments so I don’t know how generalizable that is. They’re interesting observations. I think just to step back in terms of generalities, what both of them are telling you is that the motivator, in terms of getting vaccinated, is perception of personal risk. Both of these women are telling you that I do or don’t get immunized because of the risk to me as an individual. One of them is telling you “well, I am not at risk for any of these things because I was born in India” and the other is saying “well, I am invulnerable to the flu”, so right there, that’s consistent with what a lot of research that’s out there on what drives people to get immunized is perception of risk to self, which is great. But you imagine vaccines, they’re entities that do different things: they act both in the level of the individual and they also acutally act in the level of the population. Do you know what I mean by that?
Dr: Have you ever heard of “Herd Immunity”? So there’s this issue that if you are not particulary concerned if you’re gonna get sick and if you get sick, you’re not gonna get that sick and it’s not worth it for you to go over to student health or to your doctor’s office, or in my case, you’re not gonna bother going to employee health to get immunized. You may very well be right in terms of yourself as an individual. The difficulty is that what we wind up with is called, and the economists call this, “The Nash Equilibrium1”. Have you come across that one?
Dr: Nash Equilibrium or “race to the bottom”—prisoner’s dilemma. There are situations where everybody acts in a way that makes it worse for everybody. For example, the arms race. I grew up in the 1970s-1980s where there was a nuclear arms race between the United States and the Soviet Union. The idea would be, you know, they’re spending billions of dollars in nuclear weapons. If neither of them had nuclear weapons, then neither of them would have to worry and they could save all this money. It would be better for everybody for neither to have nuclear weapons. But if neither had nuclear weapons, that motivates the one side to have nuclear weapons because they now have an advantage, which means the other side need to have nuclear weapons because if you don’t have them, then the other side has the advantage. So you wind up with everybody being in more danger and spending more money than if everybody cooperated.
And this sort of Nash Equilibrium is a property of game theory2 which describes, in economics, how people act. So we have game theoretic considerations with immunization where if you don’t percieve yourself to be at particular risk and you also perhaps think other people should get immunized. That’s gonna confer herd immunity on the population so you’re gonna have minimal transmission of measles, mumps, rubella or what have you. And you’ll also be protected because other people are getting immunized, so why would you bother, if you don’t perceive yourself at risk?
And that’s the kind of situation we’ve had for about 20 years or so. If you can imagine yourself in that situation, it doesn’t take much to tip the balance to a point where these diseases, where we’ve largely eliminated through immunization start to come back and that’s exactly what has happened over the last 5 years.
It’s hard to know exactly the degree to which Andrew Wakefield3 and the autism scare4 bear responsibility for this but following on that scare, you’ve got a lot of people looking around going, “well, you know, I don’t see measles, I don’t see mumps, I don’t see rubella, and my kids could get autism if I get them vaccinated. So, for me, the balance of risks and benefits of getting vaccinated are all out of whack and I’m not gonna get vaccinated.”
So, in Toronto and in Canada, England, United States, Australia, France and any high income countries that had these issues under control, what we’ve seen is a lot of parents have pulled back on immunization against childhood diseases which lets these things take off again. So it’ll correct in the next five years because now people will say “Oh well, measles really does happen and the kids did get sick from measles, so I will have my kids get the shots.” Things like that will happen and what it’ll do is reinforce the importance of vaccination.
But for us in public health, the difficulty is that the goods we’ve produced, which is herd immunity, which is the community part of the benefit of vaccination when we do our jobs really well that manifests as nothing happening. So people tend to say ”why are we giving you guys money? Nothing is going on! There is no measles, there is no mumps.” So our response really should be “exactly! That’s what you’re paying us to do, to make sure that nothing is happening. That’s the good that we deliver.
K: No news is good news.
Dr: Exactly. And people have talked a lot within the vaccine community but how do you message this? Well, one analogy that’s starting to get more popular is the idea that “well, do you pay for military because you wanna go invade the country next to you? Well, sometimes, but more commonly, countries have militaries so that they don’t have to use the military.” Say you invest and develop this capacity in order not to have a problem. So the idea of not having military is not so that you’ll have a war, it’s so that you’ll not have a war. We need to start claiming these kinds of metaphors for public health because we haven’t done a good job explaining to people what it is that we’re up to in terms they can understand.
K: So, we’re talking about diseases coming back because the herd immunity is slowly dissipating and that there’s gonna be comebacks. What kind of comebacks? What have we seen?
Dr: We’ve seen all of them! You know all of the big childhood diseases that are highly infectious? Well, there’s a relationship between how infectious a disease is and what fraction of the population you need to vaccinate to get herd immunity. Things like measles are so infectious that you probably have to immunize about 95% of the population to keep measles from coming back and we’re probably below that now in Toronto. You know, I just came back from a research meeting in France and I was in the city of Lyon and they said, “Hey, do you guys ever see measles in Toronto? Because we’ve got an outbreak in France.” And I said, “Well, yeah we’ve had an outbreak this past year in Toronto.” Then I went to Paris, and my colleague in Paris. They’re a little busy because there’s a big measles outbreak in Paris.
The same thing is happening in Australia, the same thing is happening in England, in Israel, in New Zealand. All these countries that had made these investments and have effectively eliminated all these diseases are starting to see them come back. And they come back in the order you’d expect which is: the diseases that are most infectious come back fastest and measles is the most infectious thing there is so, the usual estimate is that if you have a population that is totally susceptible to measles and you put an infectious person in that population, that one old case will make 15-20 new cases before they get better so it’s hugely infectious. By contrast, SARS for example, was about 2 new SARS cases for every old SARS case, so much less infectious.
K: You said that, with the herd immunity nothing happens, but that’s also starting to fade. Do you think that Torontonians would need to really see the result of this? Does it have to come to the outbreak before they start to get back on track with immunization?
Dr: Yeah, I think it’s somewhat predictable. There’s actually a quote in a french novel called “The Plague” by Albert Camus where he says that the people think that plagues and wars that happen in another time don’t happen in their own time. I think it’s very wise. People don’t like to think about horrible stuff and if it’s not going on, they think they’re invulnerable. And this is my opinion, but it often takes a scare to change their behaviour.