The Science of Vaccine Acceptance

January 22, 2021

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Saad B. Omer, MBBS, MPH, PhD, director, Yale Institute for Global Health; associate dean (global health research); and professor of medicine (infectious diseases), discussed the science of vaccine acceptance: including the consideration of thoughts and feelings, attitudes, and biases; trust, social norms, beliefs, experiences, and fears; and moral values, ideology, identity, and worldview.

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00:00So I'll be talking about
00:02the science of acceptance,
00:04and just to Orient everyone that
00:06we have a set of interventions.
00:09But one way of thinking about vaccine
00:12acceptance is that it's a Russian dog model,
00:15and so some of us have been proposing this.
00:18And then it's used by several entities
00:21to think about this is that you have
00:25thoughts and feelings that overlay
00:27our attitudes and cognitive biases.
00:30That sit on top of our trust social
00:32Norm believes experiences and
00:33underlying all of that is moral
00:35values and ideology and worldviews.
00:41And so therefore vaccine
00:42hesitancy is complex and nuanced.
00:44So before we go to it,
00:46we just you know,
00:48why do we worry about vaccine hesitancy?
00:50Generally speaking,
00:51so these are data from measles.
00:55That looked at the post elimination
00:58scenario in the US of what was happening
01:01in terms of measles Epidemiology.
01:04After you know the endemic transmission
01:07was illuminated from this country
01:09and we showed that a significant
01:12proportion as much as 69% or
01:15approximately 70% of the cases of
01:17measles in this country in the post
01:21elimination area era were coming from
01:23those who were non medically exempt.
01:27And this of those who are
01:29eligible to get vaccinated,
01:30even if you account for those who
01:33were too young to be vaccinated
01:35when they got the infection,
01:37we were getting 43% of all those cases and
01:40so forth so far as measles is concerned.
01:43That is true for a lot of a few
01:46other vaccine preventable diseases.
01:48That vaccine hesitancy is the single
01:50most preventable cause of of cases of a
01:53lot of these vaccine preventable diseases.
01:56Then we did.
01:57Another analysis where we looked at.
02:00We created this cumulative
02:02epidemiological or epidemic curve
02:04and we found that vaccine refusers
02:07were disproportionately represented
02:08in the early parts of epidemics.
02:11In the post elimination era for Mesos,
02:14and they were providing that
02:16critical mass that tender to start
02:19the fire in a lot of these places,
02:22and therefore these clusters of vaccine
02:26refusers were driving the overall.
02:29Allergy So what are some of
02:31the ways of doing it?
02:33We have been working on an one of those
02:36sort of things that some of us feel
02:39strongly about that vaccine acceptance
02:41science should be as rigorous as
02:45vaccine development and evaluation science.
02:47So as someone who has worked on trials
02:50has have LED trials vaccine trials,
02:52we try to bring the same level of rigor
02:55to vaccine communication approaches,
02:58and so we evaluate that.
03:00From that perspective,
03:01not every assessment is based
03:03on randomized control design,
03:04but a lot of these are,
03:06so one way of looking at it is to.
03:10See to talk to people's values,
03:13and there's this theory that postulates
03:15the so called moral foundations theory
03:18that postulates that we have these moral
03:22test just like our regular taste buds.
03:25You know where the combination
03:27of you know stimuli give us give
03:30each food as distinct flavor.
03:32We have these moral taste
03:35bugs that are universal.
03:36These are six moral taste buds.
03:39There's our care, harm,
03:41fairness, cheating.
03:42For example, the Golden rule in terms of
03:46fairness is universal in all cultures,
03:50loyalty and betrayal.
03:51Authority,
03:52subversion, meaning,
03:53sort of the positive valences authority.
03:56Subversion is in negative valence purity
03:59and degradation and so purity can be
04:03very secular or religious as well,
04:05and then Liberty oppression is another one,
04:09and that's why we emphasize.
04:13You know human rights almost universally,
04:16and individual Liberty and so and so forth.
04:19These values are emphasized
04:21differentially in different populations,
04:23and each stimulus triggers
04:24them differentially. So it is.
04:26Populations vary in terms
04:28of their moral matrices,
04:30and so we wanted to see our vaccines,
04:33decisions, moral decisions.
04:34So in this nature, human behavior paper.
04:37We actually were the showed that
04:40actually vaccine decisions can be moral.
04:43Decisions are often.
04:44Our moral decisions, and so this.
04:47These data show the hesitancy high
04:50versus low hesitancy above the above.
04:53The the one Odds ratio line is
04:56high hesitancy below that is
04:59lower hesitancy and we found that
05:02values of purity and Liberty.
05:05Were associated with high level of hesitancy,
05:09so people who generally emphasized
05:13purity and generally emphasized
05:15Liberty were more hesitant and
05:18similarly deference to authority was.
05:21More associated with vaccine acceptance.
05:23So these things were helpful in
05:26developing further interventions,
05:27and I'll give you an example
05:29of one of those interventions,
05:31and the idea is not to change
05:34people's values.
05:34It's not.
05:35I would postulate that it is not our
05:38place to change people's values.
05:40The key is to speak to people's values.
05:43So we did this randomized control trial,
05:46for example,
05:47where we said that young adults
05:49who missed their vaccines.
05:51In teens and now you know that HPV vaccine.
05:56IS has sub optimal uptake in this
05:59country and actually many countries
06:01and a lot of teens missed their
06:03doses and then they get to be young
06:06adults and they get to be of college
06:08age and people have tried in that
06:11group to talk about that a cancer,
06:13salient message and so talking about
06:15cancer and cervical cancer and
06:17treat and messaging through that.
06:19I think overall it is a very good.
06:22It's a very good and reasonable strategy,
06:24but in a lot of places when you
06:27have tried that.
06:28There's a huge chunk of people,
06:31especially young adults,
06:32who do not respond to that message,
06:35so we did a trial where we showed
06:38people images of genital warts so
06:40it's a less severe outcomes and
06:43had a veneer to go with it that
06:46focused on violation of purity and
06:48what we found that compared to the
06:51control group we had 20 percentage
06:53points absolute percentage points.
06:55Higher impact of this message
06:57in terms of peoples.
06:59A willingness to accept the HPV vaccine.
07:03And so then one policy tool
07:05is mandates or requirements,
07:07but the way we think about it is
07:10whether they can be used as behavioral
07:13interventions just to remind everyone
07:15for childhood vaccination.
07:17School immunization requirements
07:18are based on state laws.
07:21They have played a major role
07:23in keeping rates of vaccine
07:25preventable diseases low,
07:27but they allow for three types of exemptions,
07:30means medical,
07:31religious and personal beliefs
07:33or philosophical exemptions.
07:34And there's a lot of heterogeneity
07:37across different states,
07:38etc and these.
07:41Requirements are some places allow
07:43unknown non medical exemptions,
07:45others allow only reduce religious
07:47exemptions and and a few others allow
07:49religious and philosophical exemptions.
07:51This is a slightly dated map but
07:54I'm showing this because you know
07:56some of these contracts were used in
07:59our analysis and this one where we
08:02showed that not only the different
08:04kinds of exemptions we are,
08:06you know 8 nine years ago showed that
08:09there was a lot of heterogeneity.
08:12In the kinds of exemptions that
08:15each state was implementing,
08:16and so these data were initially published
08:19in the New England Journal of Medicine.
08:22But it has been updated since.
08:25So based on the new information,
08:27but essentially there was substantial
08:29activity based on what are the
08:32bureaucratic requirements to obtain
08:34the vaccine exemption in each of these
08:37States and what we found was that
08:39the rate of pertussis in this case,
08:42or whooping cough.
08:44Was associated even after adjusting
08:46really aggressively accounting
08:48for state level differences was
08:50associated with how easy it was to
08:53get an exemption an so if you have a
08:56pathway where your default option if
08:58you are moving people away from non
09:01vaccination to vaccination it not only
09:04has an impact on your immunization
09:06rates but also on disease rates.
09:10These rates are changing and we
09:12found that in a subsequent analysis
09:15that you have states that allow
09:19philosophical exemptions had the
09:21highest rates of non medical exemptions,
09:24but states that had religious only
09:27exemptions were catching up and the
09:30other thing we found actually this
09:33was earlier on in a 2000 union Journal
09:36paper where we describe that in various
09:39states there's substantial geographic.
09:41Heterogeneity in in exemption rates,
09:44by County,
09:45by subregion,
09:46and so it's important to keep.
09:49Keep in mind that state level rates
09:53themselves are not sufficient to account
09:56for disease risk at the lower local level.
10:00Because it's these clusters of refuzors
10:03that are driving a lot of these outbreaks.
10:06So we had a natural experiment in
10:08California where three in policy
10:10interventions were implemented.
10:12The first one was an implementation
10:14of a requirement to say that if you're
10:17going to get a non medical exemption,
10:19philosophical or religious exemption,
10:21you have to have a requirement.
10:23You have to have a physical health
10:26care provider consultation and then
10:28you have to go through a process
10:30someone explaining to you what are
10:32the consequences of your action.
10:34Then the other one was this conditional.
10:37Mentoring program where they crack
10:39down on this provision better.
10:40Even if you hadn't provided proof
10:43of exemption or vaccination,
10:44as schools would allow you temporarily
10:47and or conditionally and then there
10:49was this famous blog called SB 277 that
10:52illuminated all non medical exemptions.
10:54What we essentially found and without
10:57going into too much detail that
10:59there was a replacement effect.
11:01So non medical exemptions did go
11:03down but there was within 2 years
11:06a near total replacement.
11:08Of those who work,
11:10seeking not just medical exemptions,
11:12but those who are just kind of ignoring
11:14the law and those who were home
11:17schooling or finding other pathways
11:20of stepping away from the law itself.
11:22And so that was concerning.
11:24And we also found that in California,
11:27subsequent analysis that came
11:29out in 2019 that this law
11:31did have an impact on the clusters of,
11:34even though there was a
11:37replacement with the third.
11:39Legal intervention of eliminating
11:40all non medical exemptions.
11:42It did reduce the clustering of,
11:45or illuminated some of the
11:47clusters of vaccine refusers.
11:49So we now propose based on this
11:52Goldilocks approach not too hard not
11:55to called use of mandates and described
11:58in Nature best practices around it.
12:01Essentially set out the criteria based
12:03on which states should consider or
12:06countries should consider using mandates.
12:08And when they use it,
12:11it should be paired with soft penalties
12:13rather than hard draconian measures.
12:16And in the context of COVID-19
12:18we laid out in back in July and
12:21Union Journal the criteria for.
12:26What do you think about like when entities
12:29are imposing and considering mandates,
12:31they should meet six criteria that
12:34ensure that there is access there is.
12:37You know some behavioral
12:40principles that are followed.
12:42So there are several key
12:45challenges in a COVID-19 vaccine.
12:48Acceptance and we did with you
12:50with colleagues that have college.
12:52We did an experiment where we found
12:54that if the approval had happened
12:57and this was done in August,
12:59September before the election,
13:00one week before the election,
13:02the uptake and confidence in vaccines
13:04would have been much lower and
13:06compared to a December approval.
13:08So this would help us going forward because
13:11it ended up being a December authorization.
13:14We then found that elite so-called
13:16elite endorsers like Doctor Fouchy.
13:18Will, if they are negatively
13:20endorser vaccine,
13:21then we can forget about it.
13:23But if they positively endorsed the vaccines,
13:25then it will move people both
13:27Democrats as well as Republicans,
13:29although Democrats would be moved
13:31a little bit more in terms of
13:33increasing their uptake and confidence.
13:35And we also highlighted the
13:37value of bipartisan endorsement.
13:39So these recommendations.
13:40The preprint was available earlier
13:42on the paper came out more recently,
13:44but this was we shared these finding on
13:47an ongoing basis with various policy makers.
13:50We also identified the using modeling
13:53and using the data we collected
13:57in May we we also identified the.
14:01The characteristics of high vaccine
14:04refusal refusal so that we can target
14:07a lot of these interventions and one
14:10of the other things that we're doing
14:13with the colleagues at Hill College
14:16and Baconi in Italy is looking at
14:19behavioral policy level behavioral
14:21decisions meaning when to give
14:23vaccine to others or went to support
14:26external programs and we're finding
14:29that it is in our indicted self.
14:32Interest and not just to support building
14:34up of vaccine coverage in this country,
14:37but to also support other countries.
14:40And sometimes there will be.
14:43Total level of coverage.
14:45The marginal value of supporting
14:47other programs would be so much
14:49that that would become a pretty
14:52high priority and there are few
14:54sources that we have generated.
14:56Resources we have generated for messaging,
14:58so this one is a messaging guide
15:01with UNICEF that we developed and
15:03this is with WHO that we developed
15:06an overall acceptance and uptake
15:08of COVID-19 vaccine paradigm that
15:11focuses on the whole 360 degree
15:13behavioral insights based.
15:15Framework we are also creating this
15:17vaccine demand Observatory with
15:19a few partners including UNICEF,
15:21First Draft and an entity called PGP,
15:23so I'll pause here and I think
15:26my 15 minutes are up.