- Welcome everyone to Wednesday Nite @ the Lab.
I'm Tom Zinnen.
I work here at the UW-Madison Biotechnology Center.
I also work for UW-Extension, Cooperative Extension.
And on behalf of those folks and our other core organizers,
Wisconsin Public Television, Wisconsin Alumni Association,
and the UW Science Alliance.
Thanks again for coming to Wednesday Nite @ the Lab.
We do this every Wednesday night.
50 times a year.
Tonight it's my pleasure to introduce to you Malia Jones.
She works at the Applied Population Lab
which is right up the street here.
The Applied Population Lab is part of both UW-Madison's
College of Agriculture and Life Sciences
and UW-Extension Cooperative Extension.
Malia was born on Kealakekua,
on the big island of Hawaii.
On the Kona side.
She grew up in Philadelphia
and Malvern, Pennsylvania,
which is where she want to high school.
Then she went to Washington, D.C.
to go to undergrad at the American University
where she studied philosophy,
religions and ethics.
(laughter)
Then she went to University of California Los Angeles
to study public health where she got both
a Masters of public health and a Ph.D.
Then she went over to the dark side
at the University of Southern California.
Where she did a post-doc.
And then two years ago,
2015, in July,
she came here to UW-Madison and UW-Extension.
She's going to talk to us about one of the most intriguing
public policy issues over the course
of my professional career in science outreach.
And that is the vaccination and anti-vaccine movement.
She's here to talk to us about increasing numbers
of parents are refusing to vaccinate their kids.
Should public health be worried?
And as we've been saying the last four weeks,
"Yes."
We're helping you out there.
- [Malia] You're worried. (laughter)
- Please join me in welcoming Malia Jones
to Wednesday Nite @ the Lab.
(audience clapping)
- Thank you. Thanks for coming tonight.
So what do you think? Are you worried?
- [Audience] Yes. - Anybody not worried?
Nobody in this room.
So I'm gonna talk as Tom said about
parents who don't want to vaccinate their kids.
And who they are.
A little bit about myself to get you started.
What I study in general is how people sort themselves
into geographic space.
And so what I'm really interested in
in terms of people who don't want to vaccinate their kids
is how tightly clustered are they?
In school settings, and in neighborhood settings.
And why do we see that kind of clustering arise?
I'm gonna focus mostly on California
because we have really great public data from California.
Although Wisconsin is actually taking some steps
to make more data public at the school
and school district levels.
So I will briefly mention that a little bit at the end.
But these trends actually apply nationwide.
California is sort of on the forefront of the
vaccine refusal trend.
But we're seeing increasing rates
of vaccine refusal nationally.
So you can think about these things happening
pretty much everywhere.
So just a little bit of background
to get you started as I'm sure you all know.
Starting in 1798 when the Smallpox vaccine was discovered,
we have been inoculating kids against infectious diseases
and at this time,
there's quite a series of infectious diseases
that kids are protected from by vaccines.
And just to give you some background info
on how effective those vaccines are,
I have a couple of charts here
that show the rates of different diseases
through time in the United States.
And then each of these charts shows how those diseases
really drop off after the introduction of the vaccine.
So, Polio was extremely prevalent in the United States.
Especially beginning around in the post-World War II era.
It was a huge social and health issue.
How many of you remember the Polio days?
Yeah, so when the
inactivated Polio vaccine was introduced
and then the oral Polio vaccine
a couple of years later.
Those were required for school entry in many places
and Polio rates just dropped,
completely bottomed out and now we have no cases
of Polio in the United States.
We're working on worldwide eradication of Polio
at this time.
Similar for Pertussis.
In the mid-1940s, a little bit earlier,
the Pertussis vaccine was licensed and introduced
and Pertussis rates have declined steadily.
You can see a little hint of what I'm going
to be talking about later here.
Pertussis, or Whooping Cough, as it's colloquially called
has actually been increasing again
in the most recent years.
And then, Measles is another major infectious disease
that used to cause hundreds of thousands of cases
each year in the United States.
And when the series of Measles vaccines was introduced,
the rate of Measles infections dropped off
precipitously.
And this is just sort of a summary
that compares 1900 to 2000 levels
for a variety of different infectious diseases.
And you can see
Measles up there in 1900
caused about 500,000 cases
of childhood Measles in the U.S.
And today, it's in a bad year,
it's really just about 500 or so.
The levels are so low in fact
you can barely even see those 2000 bars.
Smallpox having been,
and Polio also having been completely eradicated.
The vaccines are really effective,
but how do we make sure everybody gets them?
One of the primary mechanisms for ensuring
good population coverage of the vaccine
is through school entry mandates.
So, in the United States,
all 50 states have some kind of requirement
that children be vaccinated in order to attend school.
The first of those mandates was introduced
a really long time ago in Massachusetts, 1855
passed the first school entry vaccine mandate.
And today, as I said,
all 50 states, DC and Puerto Rico have mandates.
All but three of those states
allow some kind of exemption
from the mandated vaccines series.
And there are two kinds of exemption
that are common.
Religious exemptions
and what's called a personal belief exemption.
Or what you'll see in a lot of my charts
referred to as a PBE, okay?
So the three states that are exceptional here
are California,
West Virginia,
and Mississippi.
So California is actually really interesting
cause it's the first state in a long time
to pass a new stricter vaccine mandate.
So last year was the first school year
that no personal belief or religious belief
exemptions were allowed in the state of California.
If you want to be exempted from vaccines
in the state of California, you need a medical exemption.
Which of course you have to get from a doctor,
and typically the doctor has to agree
that your child is allergic to the vaccine.
Or has some immuno-compromised issue
that cannot get the vaccine for medical reasons.
So I'm gonna be looking closely at this policy change
and how it has affected the vaccine rates over time.
That personal belief exemption in California
used to be, before it was eliminated,
extremely easy to obtain.
And in fact, in Wisconsin,
it's similarly very easy to obtain.
All you have to do to get an exemption,
this is the immunization record
that the school keeps for each child,
and a parent who doesn't want an immunization
just fills this thing out, hands it in.
A parent who wants an exemption from the vaccine,
before the policy change, just turned that same form over
and signed the back.
I want an exemption from this vaccine mandate.
Handed it in and that was the end of the story.
And Wisconsin it's similar.
All you do is sign a brief affidavit
that says that you do not want to comply
with the mandated vaccines.
In 2013, a law was passed in California
that made this a little bit harder.
Instead of just having to sign the affidavit,
you also had to get a note from a doctor
saying we have discussed the risks
of not vaccinating this child.
And then in 2016, the most recent school year,
all of the exemptions were eliminated.
So there have been two pretty rapid policy changes
in a row, in California, in order to try and
reduce the number of exemptions from school entry vaccines.
And what are we talking about here?
These are the required vaccine series.
In most states it includes Measles, Mumps, Rubella,
Varicella or Chicken Pox, Polio,
Human Influenza Type B,
Hepatitis A, Hepatitis B,
Diphtheria, Tetanus, Pertussis,
and then in a few states,
very controversial HPV vaccine is also being required.
Not in California.
So, why is this level of vaccine coverage
really important in order to protect the population health?
The issue here is this thing called herd immunity.
Which I'm sure many of you have heard of before.
But just to catch everybody up,
herd immunity is the risk that each vulnerable person
has of acquiring an infectious disease.
It's based on their probability of bumping
into a person who has the disease.
So if you're in a very crowded environment
and everyone is susceptible.
And you would choose one person who has the disease,
then everybody is gonna be at risk
of contracting the disease, right?
If you're in the same crowded environment
and most people are vaccinated,
or maybe they've had the disease before,
so they're not susceptible to catching it,
then the probability even with a lot of contact
between people,
the probability that that infected person
is gonna bump into someone who's susceptible,
is low.
And that actually prevents the disease
from getting enough cases going in the population
to create this sort of wave of infection,
and cause an outbreak.
So herd immunity doesn't actually protect individual
people directly,
it protects the whole population.
It's a statistical phenomenon.
And this graphic here
is sort of, illustrates this point.
So, I'll just go over.
In this top case, no one is immunized.
Okay, the blue people indicate a person who is susceptible.
They're not immunized, but they're healthy.
And then the red people here
are people who become infected.
And you can see that because of this high probability
that infected person is gonna come into contact
with a susceptible person,
the whole population is at risk.
This is sort of a mix.
Some of the population are immunized.
There's still a high probability
that this infected person could bump into
a susceptible person.
And so the whole population is still
at pretty high risk.
And in this case,
you have the green people who are immunized but healthy.
They are not susceptible to the disease.
They're sort of providing this buffer
between the susceptible people
and the infectious people.
So that the probability that they'll bump into one another
is low.
Okay, this is a really a key concept
for understanding why it matters so much
when a few people don't vaccinate their kids.
There are some other factors besides just the number
of people who are vaccinated
in what determines how many people need to be vaccinated.
And those are sort of summarized under
this thing called R not.
R not is just a, it's a summary statistic
that if the number of people on average,
who will get the disease from each person who has it.
So if I were to contract Measles,
R0 (R not) not would be the average number of people
who get it from me.
And that depends on several things,
including how many susceptible people are there
in the population.
It includes how much contact do they have with each other.
Under a quarantine,
people have reduced contact with each other.
So R0 (R not) can be lowered that way.
It also depends on some properties of the disease.
Like its mode of transmission.
How hard is it to catch?
Measles is very easy to catch
because it's an airborne transmission disease.
It can hang in the air
being infectious for hours after an infectious person
has left the room.
So it's very easy to transmit.
A disease like Ebola actually
is quite difficult to contract.
You need bodily fluid contact
to contract Ebola from a person.
So that's one factor.
How likely is an exposed person
to develop the disease?
Some diseases don't always turn into a full-blown case.
And then, the last thing is for how long
is an infected person walking around spreading the disease?
So it's a time element to the question.
In the United States,
with these childhood infectious diseases
that are pretty rare,
the probability that kid gets sick
and goes to the doctor and then the doctor
just doesn't know what they're looking at
and doesn't diagnose them properly
actually plays into this.
So they could be walking around with Measles
and not know it just because doctors aren't trained
in diagnosing Measles in the United States.
So these are all factors that affect--
that are sort of disease specific,
population specific that affect how much
of the population needs to be covered by a vaccine
in order for it to be really effective.
And produce herd immunity.
So this is a graphic produced by the Guardian.
It's a really neat interactive graphic.
And I put the link up there
so that you can go look at it in its interactive form.
But it gives you a sense of sort of the likelihood
of contact and the likelihood of spread of disease
under different rates of vaccine coverage.
So this top one here says you have 10% vaccination rate.
Those are the blue dots.
Susceptible are the yellow dots.
And then the red dots are the people
who have become infected.
So you can see a low vaccination rate produces
a really high infection rate for Measles.
Somewhere in the 90 to 99% range,
you get really good herd immunity for Measles.
And infected people are unlikely to give
the disease to susceptible people.
So because of these variety of factors,
different diseases have different thresholds
for herd immunity.
Polio, it's 80 to, and they're also estimates.
R0 (R not) not turns out to be quite a hard thing to estimate.
Because there all these unknowns.
Like we don't know how many susceptible people
that are in the population.
Immunity declines with age for some diseases.
And sometimes vaccines aren't as effective
as they once were. And blah, blah, blah.
So, there's a range here.
So Polio, 80 to 86%.
Diphtheria's about 85.
Mumps somewhere in the 80% range.
Rubella, it's about 84%.
Pertussis and Measles are the diseases
that you're hearing a lot about
on the news in terms of having a lot of outbreaks.
And I think the reason for that is
because they have really high thresholds for herd immunity.
Pertussis, it's in the low 90s somewhere.
And Measles, this is the low estimate,
is 95%.
Some people say it's more like 98 or 99%
because it's just so easy to transmit.
So I think that the reason we see these
outbreaks of Pertussis and Measles
right now is because we're sort of bumping up against
that herd immunity threshold
in some subpopulations in the United States.
Where vaccine coverage is declining.
And so you can see this in the figures.
This graph shows that vaccine coverage
and personal belief exemption rates
in California Kindergartners.
And I have 15,
in this case I have 13 cohorts of data.
So this is 13 different Kindergarten classes
in the state of California.
Each class is about 600,000 kids.
And you can see what happens over time here.
The pink line is the exemption rate.
And so, in 2001, the exemption rate,
that's this axis over here,
it was about 1 1/2 percent
personal belief exemption rates.
And then, each year going right up this graph,
and really starting to sort of take a new shape
in 2007, 2008 the exemption rate starts to go way up.
Until in 2013, it was over 4% personal belief exemption rates
in the 2013 Kindergarten Cohort, which is high.
So 4% of kids in Kindergarten had
some kind of exemption on file.
Didn't have or --
Any diseases or were exempted from at least--
Any vaccines or were exempted from at least one vaccine.
And then you can see if you were wondering
well, how do exemptions match up with specific vaccines?
You can see that the specific regent vaccination
rates were declining at the same time.
So this exemption rate is a pretty good metric
of the actual vaccine coverage
in the population.
And then we saw,
we've seen a lot of recent outbreaks.
Many of you have probably see these on the news.
And that's why you all raised your hands
when I asked you if you're worried.
This was a really, really high profile one.
The Disneyland outbreak in December 2014.
An intentionally unvaccinated person
likely contracted Measles
in another country where it is still endemic,
and then went to Disneyland.
And of course, there's a ton of contact
between people at Disneyland, right?
And gave Measles to,
ultimately, the outbreak spread to 141 people
all across the nation, in several states.
I was living in California at the time.
I actually had a one year old, who was due for his MMR vaccine
right in the middle of this outbreak.
And ironically enough, he was late getting his MMR vaccine
because I was like, no way,
I'm not taking him to into a doctor's office right now.
(laughing)
So the Disneyland outbreak was a really high-profile case.
It has been in follow up studies,
it has been linked to,
expressly to low vaccination rates in the population.
Though this is an excerpt from a JAMA Pediatric study
that shows the estimated effect of reproductive number
that's that R0 (R not) number that I was just talking about,
assuming a number of different sort of population level
coverage of the MMR vaccine.
And what they found was that if we had had
really good vaccine coverage in California
during the Measles outbreak,
it never would have spread to 141 people.
Okay, so the fact that it spread as far as it did
suggests that MMR coverage is much lower
than where we would want it to be.
Most recently, I'm sure you heard about earlier this year,
there was a large outbreak of Measles in Minnesota.
And this particular one was really interesting
because it was focused in a
small socially-isolated community of Somali immigrants.
Who had really low vaccination rates
for MMR specifically.
And the disease ultimately spread to
I think it's 71 people.
And you can see in this graph right here
that the immunization rate for Minnesotan born children,
all Minnesotan born children,
as opposed to Somali descent children,
there's a huge gap between the immunization rates
for this group and for the general population.
So there's something going on in this particular community.
They're a really tightly clustered group of kids
with low vaccination rates.
And they had this Measles outbreak after
a foreign case came in.
So here's sort of a summary.
We also have had a resurgence of Pertussis
in recent years.
And that's also thought to be connected
to declining vaccine coverage.
As Tom mentioned in my intro,
I once upon a time studied ethics.
And I find this part of the issue really interesting
I think for that reason that
the vaccine coverage in the population
is a great example of this concept
called the Tragedy of the Commons.
And it's this concept that when
community interest conflicts with individual interest,
then we have to produce the interest of the community
by putting controls on individual behavior.
Most people will choose their own interests
over community interest.
And so we have to control somehow the behavior
of individuals in order to benefit the community
as a group.
Herd immunity is the common good.
Vaccines on an individual basis
are not without risks.
There are risks associated with getting vaccines.
Some of them are real.
And some of them are perceived risks.
And I'm going to talk a lot more about perceived risk
and how that's changed in recent years.
And so what we see happening
is that as disease rates decline
following the advent of the vaccination era,
those risks of getting the vaccine sort of grow larger
in the public mind, right?
And as parents weigh the risks and benefits of vaccinating
their own child,
the perceived risk of vaccination
seems sort of outmoded,
larger than it used to be.
Relative to the perceived benefit to the community.
So, I don't that parents who don't want to vaccinate
their kids are crazy or uninformed
or any other sort of pejorative.
I think that they're making a decision based
on bad information.
And the decision is that the vaccines are somehow
riskier than this counterfactual scenario
where they don't vaccinate and they probably
will never be exposed to disease, right?
But it's hard I think for people to sort of scale that up
and think about the population level consequences
of everyone behaving that way.
Where you really get into this tragedy
of the commons situation.
So eventually what happens people make this
kind of risk benefit calculation on an individual basis
and then herd immunity declines
because they're deciding not to vaccinate.
So why are some kids not vaccinated?
Some kids are allergic to vaccines.
Particular ingredients of vaccines
or the way that they're produced.
They might be immuno-compromised
and so they're not eligible to get a vaccine.
There are a number of legitimate medical contraindications.
Some kids aren't vaccinated because they don't
have access to vaccines.
And that can include the cost of getting vaccinated.
Some people have said to me,
"Well, the federal government provides free vaccines."
And that's true. But they do that at free clinics
where you have to wait forever to get them.
And not everybody has time
to stand around waiting to get their child vaccinated.
So there's also the opportunity cost.
Availability of vaccines has been an issue
at various times through history.
And then of course,
availability of appointments to get your vaccines on time.
Some people don't vaccinate their kids
for religious reasons.
And I'll talk a little bit more about that in a minute.
And then we have this other group,
personal belief refusers or noncompliers.
And I think that this can be divided into two subgroups.
Whom I like to call naturalists and Libertarians.
And I'll describe each of those in just a minute.
So where do these sort of fears about vaccines come from?
It's a much longer history.
There were people who thought vaccines were too risky
when the Smallpox vaccine came out.
There have always been people who have thought
that vaccines are too risky.
But in 1998, a former doctor named Andrew Wakefield
produced a study. It was a pretty small study.
And it was published in the Lancet,
so it's quite high profile,
that linked the MMR vaccine to autism.
And this was sort of picked up by
subgroups within the anti-vaccine movement
and distributed widely as truth.
And then later on, more recently,
it came out that Andrew Wakefield
had invented the data he used
to make these claims.
The study was retracted
and he was stripped of his medical license.
But it took about 10 years for that to happen.
And I think by that time
a lot of the damage had been done.
There were some other really high profile
celebrities and doctors who also took up this cause
that vaccines are too risky
and specifically may be linked to autism.
And really spread the word
that this link exists.
Which to be clear with everyone in this room,
there is zero evidence that there is a link
between MMR and autism.
So one of these folks is Jenny McCarthy.
She's been a very outspoken advocate of vaccine choice,
or refusing vaccines or eliminating them.
Dr. Sears is also a proponent
of not entirely missing vaccines,
but doing them on a delayed schedule.
So the children are,
get less vaccines at one time
or are exposed to less disease agents
at one time during the vaccine process.
And so there's been a lot of high profile,
public attention.
That I think really heightened parental concerns
around vaccines and helped to produce
this sort of inflated sense of risk
that parents are using when they evaluate
whether or not it's safer to vaccinate
their kids or not vaccinate their kids.
And so, the science shows that there
are actually a number of different parental concerns
that are raised.
68% of parents have no concerns.
So, about two in three parents, no concerns about vaccines.
But at least quite a few parents who have some concerns, right?
7% of parents are worried about autism
with respect to vaccinating their kids.
But an even bigger proportion are worried
about this concept of over toxicity
or immune system overload.
So somehow exposure to these vaccines
is just too much for their kids' immune systems.
And so they're worried about the safety
of exposing them.
6% of parents say that it's either healthier
to get the disease naturally or
the vaccines aren't as effective
as getting the disease naturally.
Or there's no point in getting the vaccine
because the diseases just aren't that dangerous.
So it's sort of a preference issue.
I'd rather just let my kid get Measles
than do this vaccine.
And then 7%, about an equal number of parents
cite concerns about the additives in vaccines
including aluminum, mercury,
other preservatives and so forth.
9% had two or more of those concerns.
And then these parents,
this one-third of parents who have any concerns
are somewhere between two and 20 times
higher risk of using an alternative vaccine schedule.
Or foregoing vaccines altogether.
So an alternative vaccine schedule,
I should back up a little bit, means you don't do it the way
the CDC and the American Academy of Pediatrics recommends.
You space out the vaccines. You do them one by one.
You do them over a much longer time window.
So instead of over two years,
you might do them over ten years.
Something like that.
So another thing we know about vaccine hesitancy.
It is not a binary outcome.
So this idea of there being anti-vaxxers.
It's a little bit of a misdirect
because it's not just an either-or situation.
Lots of parents have some concerns
but go ahead and vaccinate anyway.
Some parents have some concerns about one vaccine,
but they're totally fine with all the other vaccines.
They might just delay the vaccines by a little bit.
So there's a range.
Parents can be located on a spectrum
in terms of how they feel about vaccines.
Also, parents, this is a little bit obvious,
but like many things,
was a surprise to social scientists,
parents don't, their attitudes are not fixed.
They evolve over time.
So they might have been fine with vaccines
for their first child,
but their second child doesn't get any.
Or maybe the other way around.
Parents change their minds about these things.
Also, a lot of the work has looked at
the vaccination status of children when they enter school.
But actually this decision making process begins
much earlier in pregnancy.
So when we think about what do we do about parents
who don't want to vaccinate their kids,
we really need to back up and think
about much earlier on in the decision-making process
than the science has done so far.
And then as I said, vaccination itself is not binary.
Lots of kids are partially vaccinated
or they're delayed in vaccinations.
There's sort of a range of different outcomes there.
And here's just an article that sort of talks about
the different degrees of vaccine hesitancy
and classifies them along a spectrum.
So we have people who range from I love vaccines.
Vaccines are terrific.
Like me and most of the people I went
to public health school with.
That's about 33% of the population.
There are go along, get alongs.
People who just do what the doctor says.
They don't have a strong opinion.
Agnostics needs to be convinced
and sort of talked through the process.
That's about a quarter of the population.
Compromisers who can be talked into doing some vaccines
maybe on a different schedule.
That's around 13%.
And then, this is my term, I call them true believers.
The people who will not vaccinate their kids
under any circumstances.
And that turns out to be a really small fraction of people,
2.6%.
But when it comes to a disease like Measles,
that's an important fraction, right?
Cause we're talking about that really high threshold
for herd immunity.
And then there are degrees of responses as I said.
Some people who don't vaccinate, they partially vaccinate.
They ask questions.
And there's a fair amount of science out there right now
in the medical community about how to deal with a parent
who has vaccine concerns.
Because this study found that about 85% of providers
have a parent who refuses a vaccine each year.
So this is really common for physicians
to run into in their panel of patients.
There was an interesting issue that came up a couple years ago
as this vaccine refusal trend started to crest,
what should doctors do about a parent
who doesn't want to vaccinate their child?
Should they dismiss them from their practice?
Or keep them and keep working on 'em?
And this actually became a medical ethics question.
And there was some really interesting work on this.
The outcome of which by the way,
was that they should not be dismissed.
They should probably keep them in their practice
and continue to talk with them.
In part because we found that effective communication
can help sort of convince a parent
that this is the right way to go.
So listening to specific parental concerns.
Responding with unambiguous information
are all sort of key for a physician-parent relationship
to promote vaccination.
So who are these folks?
Risk factors for being an access noncomplier,
someone who can't access vaccines
include health insurance status.
Not having health insurance.
Immigration status, especially being
an unauthorized resident of the United States.
Language barriers.
And then also, there's a tiny bit of evidence
out there that people who are migrant workers
are less likely to have vaccinated children.
And that might be,
it's a little unclear whether that's
their kids are actually unvaccinated
or if they just don't have the paperwork
because of their migration status
and their residential mobility.
And then people who don't have time.
As I mentioned, this is really an under studied issue,
but I think it's an important factor
for access noncompliers.
We also have religious noncompliers.
Risk factors for being a religious noncomplier
include having a fundamentalist religious belief
and being socially isolated.
So there are groups of people who live
in specific religious communities.
For example, Amish communities don't believe in vaccination.
And so you'll have a whole cluster of people
living in a pretty small social space
that have religious reasons
that conflict with vaccination.
Generally these folks are more rural dwelling.
They are lower income.
They have younger age at first birth.
They're lower education.
And then we have the personal belief noncompliers.
And as I said,
I think this can be divided into two different groups.
This is sort of qualitative evidence
that I have observed myself.
But both of these groups share some characteristics.
They're generally, they have higher education.
Older age at first birth.
They tend to be affluent and white and nonreligious.
In fact, a lot of these people would consider themselves
very science minded.
And that's one of the reasons that I say
I don't think they're uninformed.
You know, this is actually a very privileged group of people
who are making a decision that we just don't expect
as public health professionals.
The naturalist subgroup is politically very liberal
and then the Libertarian subgroup is smaller,
politically very conservative,
and very understudied.
In fact, this is just me talking right now.
There's no other science out there
on this, okay? (laughing)
So the idea, this is really a story about ideology.
And the ideology that leads a person to make
a decision about vaccinating their child.
I call these two groups the naturalists
and the Libertarians because it's not
an isolated decision when they make a decision
about vaccination.
That decision fits within a broader set of ideas
about the way they live their lives and the way they see the world.
And the naturalists in general believe that vaccines,
that the safest and best way to raise a kid
is the natural way.
And somehow vaccines have been sort of classified
as unnatural in that ideology.
Libertarians, it's a really different ideology
that leads them to the same place.
And that is that the government
should not have this authority over me.
I'm not going to vaccinate my kids
because the government told me to.
All right, so it's quite a different
sort of set of ideas that leads people there.
And we can maybe see this if we look at political maps.
This is not the same thing,
but we're talking about ideologies.
So it's a related concept.
And there is variation in California
in terms of how ideologies
pattern over space.
So we can get some hints about maybe what's going on
with these patterns of anti-vaccination
in California.
So you can see in California,
there are a lot of Democrats in California.
They are clustered on the coasts and in the major cities.
Republicans in California
tend to be in the central valley,
sort of the eastern half of the state.
This next set of maps is probably more informative.
These are people who voted Libertarian.
Not the Libertarians I'm talking about
with not vaccinating their kids.
You can see that they are clustered in these really rural
counties on the eastern side of the state.
And then the northern coast.
Green Party voters were really strongly clustered on the coast.
Especially the northern coast.
So there are a lot of things we don't know
about vaccine hesitant parents.
We have some.
There was one study that suggested
telling them about the risks of contracting
diseases actually makes them less likely
to vaccinate their kids.
Traditional public health messaging
totally ignores this variation between groups.
Like the difference between people who don't want
to vaccinate because of religious belief
and people who don't want to vaccinate
because they don't like the government telling them to.
And we have some lessons from market segmentation.
I think we really need to understand these differences
in order to target public health messaging more effectively
to these various groups.
Especially that naturalist group.
We really I think need to better understand
how people come to see vaccines
as inconsistent with the rest of their parenting ideology
in order to get them on board with vaccination.
And the approach that's actually been used in California
and elsewhere is policy.
As I said at the beginning.
We've had this series of policy change in California
to try and stem the tide of vaccine refusal.
And I think that's gonna work for some parents.
But other parents are really willing to go the distance
to not vaccinate, right?
There's a commitment that is not gonna be stopped
by a policy change.
So the problem, vaccine rates have been falling sharply.
Those rates are variable in space.
We see geographic clusters of people who don't vaccinate
their children and these pockets,
these spatial pockets
are subgroups of people who have really poor herd immunity.
Deeply compromised herd immunity.
In schools and in neighborhoods
and in some cities.
And that is a serious threat to herd immunity.
We're gonna see disease outbreaks
in situations like that as we have
in the last few years.
So here's a map that shows the personal
belief exemption rate by county in California.
And you can see that pattern of the different ideologies
that I was talking about there.
You have some counties in California
with exemption rates as high as 15%.
Especially along the northern coast here
and Santa Cruz county.
Not only that,
we have school level data on these kids.
And my colleague Allison Buttonheim and I have found
that there is tremendous school level clustering.
So those same ideologies that lead parents to make
a decision about vaccinating their kid,
also lead parents to choose a school, right?
They choose a neighborhood or a school based
on their parenting beliefs.
And so we see these really extreme rates
of vaccine exemption in certain schools
and types of schools in California.
And we measure these things by two measures.
One measure is clustering
or the probability that an unvaccinated child
is gonna bump into another unvaccinated child
in their own school.
And the other measure is exposure.
That's the probability that a vaccinated child
is gonna bump into an unvaccinated child in their school.
And that's important because vaccines don't always work.
And so even vaccinated kids are at some risk
when they encounter an unvaccinated kid.
So this figure just shows the degree
of current personal belief exemptions
is just the number of personal belief exemptions
by county in California.
And then this is the aggregation index.
That measure of clustering.
And you can see that although these larger
population counties like Los Angeles
and San Diego County don't have a ton of clustering,
there is really tremendous clustering in some
of those high-risk places.
And this is just an excerpt from the paper
where we argued that norms around vaccination
and securing exemptions are likely
to be shared in these communities.
And these ideas defuse through parent social networks
before and after the Kindergarten enrollment process.
So parents are getting the idea
that they're not gonna vaccinate their kids
from one another.
It's a very sticky idea.
And we don't thoroughly understand why it spreads so easily.
So here are the policy changes.
As I said,
the first one AB2109 required a physician's signature
for a personal belief exemption.
It allowed a free religious exemption.
So the religious exemption was still really easy.
You just turned the form over and signed it
under that law.
SB277 eliminated all personal
and religious belief exemptions in California.
There is still a medical exemption in California.
Wisconsin and many other states
have actually started to respond to these same issues
by proposing some policy change.
Wisconsin, a colleague of mine in here at UW,
who works in pediatrics infectious disease,
helped draft a bill that would have eliminated
the personal belief exemption here in Wisconsin as well.
And the bill was never heard on the floor
but it's sort of an ongoing effort
to promote policy change.
So what do we think happened in terms of prevalence
in clustering of exemptions after these laws passed?
Well this shows the pre exemption level of clustering
and rates of personal belief exemptions.
This heat map gives you a sort of more refined sense
of where the real hot spots are
in terms of clustering.
And then we asked this question.
Was recent California policy change effective?
And was it effective especially at reducing these clusters?
That's what's really important for herd immunity.
So we used data,
as I said there's great public data from California.
We have, it's actually 16 cohorts of data now
from 2001 to 2015.
For every single Kindergartner.
So it's not a sample.
It's all of them, right?
This is super confusing to reviewers of my papers.
They're constantly giving me a hard time about this.
We do have some really small population counties
where one kid can make it appear
that the exemption rate spiked for one year
and then went back down again the next year.
But that's because the denominators are quite small.
So you do see some noise in the small population counties.
We do the analysis at the county and the school levels.
And then the caveat here,
are some kids with a personal belief exemption
actually vaccinated?
Yes, some of them are.
Some of them are partially vaccinated.
Some of them are completely vaccinated
and their parents didn't happen to have
the paperwork when they came in to enroll their kid.
But we do know that they are as a group,
under vaccinated.
So this is a high-risk group.
Even if it's not sort of the maximum risk group.
And what did we see after these two policy changes?
This is the trend in personal belief exemptions
over time that I showed you before.
But now it's got a couple more years of data tacked on here.
After AB2109, there was a big drop
in personal belief exemptions
because it got a little bit harder
to get those exemptions.
That policy was in place for two years.
And then SB277 took effect
and the exemption rate for California
went all the way down to
a historic low level.
So, yes. This policy was quite effective.
What do we know about clustering though
of that 0.6%?
'Cause that could still be really important
if those parents who are willing to go the distance
are gonna go out and find a way to get an exemption.
One of the ways that we see that they did that
was that the rate of medical exemptions
has been ticking along at about 0.1%
for 20 years.
And last year it jumped up to half a percent.
So there were some parents who went
and got a medical exemption from a doctor
after SB277 was passed.
What happened with clustering and exposure measures?
Actually, not very much.
The policies did not change clustering very much at all.
The most recent data year is not on there.
The 2016 data, because California
changed the way that they mask some of their data.
And so the public data,
you actually can't calculate this measure
from the public data anymore.
So, I'm waiting for them to give me the unmasked data
to tell you what happened with clustering
and exposure in the most,
after SB277.
After assembly bill 2109,
clustering did not change very much.
So we do see this pattern of parents
who were already clustered in schools,
kids who were already clustered in schools,
and had low rates of vaccination
were still clustered in schools.
So we still have some concerns about herd immunity there.
What's sort of the upshot here?
Policy did have a really substantial impact.
Probably did not fix this problem
of parents resisting vaccines.
There's a substantial fraction of noncompliers
who took the time and effort to go get
that healthcare provider signature on their exemption form
before the exemptions were eliminated.
And now we're seeing there was a substantial number
of parents who went and found a doctor
who would agree that there's a medical contraindication
for vaccinating their child.
It's a small fraction, but as I say,
with Measles and Pertussis,
those small fractions can be really really important.
We also saw a substantial fraction of people
took that free religious exemption
under the first version of the policy change.
And yeah, clustering of exempted kids
was not greatly impacted.
Now, when you look at the Wisconsin data
and the Wisconsin proposed policy change,
we do see substantial clustering in schools
for Wisconsin vaccine rates.
So there are reasons to think that in Wisconsin
there's also substantial clustering.
There's also pockets of places
that have really compromised herd immunity.
Especially on these high risk diseases.
And the bill that was proposed to amend this
would not have eliminated vaccine exemptions in Wisconsin.
It would have like that first California bill,
it would have just made 'em a little harder to get.
So the policy approaches to this I think are,
it's a step in the right direction.
I don't think it's gonna fix things
for the most high risk groups in the population.
So a few limitations.
We don't know very much about the extent to which
personal belief exemption kids are vaccinated.
We do know that they are more likely to be under vaccinated
than the general population.
So there's some sort of wiggle in what
the real risk of outbreak is here
when you talk about exemptions versus
you look at a kid's medical records
and you know for sure whether they got a vaccine.
As I said, the Kindergarten enrollment
it's not the right time for measurement or intervention.
By the time a kid is entering Kindergarten,
they're five years old.
They should have completed this vaccine series
when they were two.
So it's just sort of not the right time to measure.
And then we really need
to know something about these parents
and what they're thinking when they evaluate
the risks and benefits of vaccinating their kid.
And we know almost nothing about that.
So that's sort of the future direction of my work.
I'm gonna try and work with some survey data
and figure out if I can tease out these different ideologies
and what the context of people's
decision making process really is
when they decide to vaccinate or not.
So here are a few conclusions.
The highest risk areas still have significant clustering
of unvaccinated children.
And yeah, we have a lot more work to do
to understand how to address these vaccine hesitant parents
and what is driving the trend
of increasing vaccine hesitancy
in California and in Wisconsin
and in the U.S.
You also see these trends happening
and playing out in Europe.
I'm sure you've seen the news about recent outbreaks there.
So my future directions.
I want to know what's happening in these high-risk areas.
I'm trying to access the Wisconsin immunization
record data to get some personal level information
about the timing of when kids are vaccinated in Wisconsin
and maybe even spatial information
about how clustered they are.
And then I'm really interested ultimately in
looking at implications of this work for HPV vaccine.
Which has a sort of a whole different ball of issues
wrapped up with it.
But it is likely going to be the next mandatory vaccine
coming along in many new states.
And ultimately what I want to do is understand how to better
target and communicate with high risk parents
with an effective intervention.
And I'm using some new methods to do this
including this really cool thing called
agent-based modeling.
Where you set up a simulated population of people
and you can give them some behavior rules
and then tell them to go interact with each other.
And you can see the patterns that emerge.
And this will give me the ability
to test my little hypothesis that says
the idea of vaccinating being too risky
is actually something that moves from parent to parent
through a community.
And that idea itself is very sticky.
And that I think would help us understand how to better
intervene and talk to these parents.
So should public health be worried? Yes.
Public health should be worried. This is a big problem.
We're gonna see increasing numbers
of these kinds of outbreaks like the one
we saw earlier this year in Minnesota.
Especially in these high risk communities
where there are a lot of unvaccinated kids.
If you have kids or grandkids
who are in a school, you can actually look on
the Wisconsin Department of Public Health data
at the school level vaccination rate
where your kids go.
So if you're curious what the risk environment
is in your kid's or your grandkid's school,
you can go look at that up
on the Department of Public Health website.
Okay.
(audience clapping)