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From the modellers’ point of view - How to communicate with the policy community? - Kari Auranen and Tuija Leino
1. From the modellers’ point of view -
How to communicate with the policy
community?
Kari Auranen and Tuija Leino
Department of Vaccination
and Immune Protection
National Institute for Health and Welfare,
Finland
2. Outline
Infectious disease modelling at NPHI/Finland
Three recent examples
Varicella vaccination
HPV vaccination
Pneumococcal conjugate vaccination
Communicating modelling results to decision
makers
Main question(s) for modelling
Some results and how they were addressed in decision
making
Lessons learned
4. Criteria for the introduction of a new vaccine
to the national programme in Finland
[1] There is a considerable disease burden
which can be prevented by vaccination
[2] The vaccine is safe on the individual level
[3] Vaccination is safe on the population level
[4] Vaccination is cost-effective
NACV
5. Varicella zoster virus
Chickenpox
Childhood disease (90% cases in children < 10y)
Virus remains latent, can activate as herpes zoster
Herpes zoster
Disease of the elderly
Encounters with varicella virus may sustain immunity
against herpes zoster
Vaccination protects from chickenpox and
(subsequent) herpes zoster
Under high coverage of vaccination, circulation of the
virus ceases
The adult population may become susceptible to herpes
zoster because lack of boosting
6. Introducing varicella vaccination?
Vaccination against varicella zoster virus has not
been part of the national program in Finland
Vaccine-specific expert group (2006-2008)
The main question for dynamic modelling
What would be the effect of varicella vaccination on
zoster incidence?
7. Three types of data
Age-specific incidence of varicella infection
At what age do individuals first encounter the virus?
A contact survey on the social mixing pattern:
”who meets with whom”
From whom do they acquire the virus?
Age-specific incidence of herpes zoster
At what age do individuals get the disease?
8. Incidence of varicella
Proportion with varicella virus
At what age do
individuals first
encounter the virus?
Age (years) Davidkin et al.
9. Pattern of transmission
Finland
70+
65-69
60-64
Age of the contact
55-59
50-54
From whom
45-49
Age of contact
40-44
35-39
30-34
do individuals
25-29 acquire
20-24
15-19
the virus?
10-14
05-09
00-04
70+
00-04
05-09
10-14
15-19
20-24
25-29
30-34
35-39
40-44
45-49
50-54
55-59
60-64
65-69
Age of participant
Age of participant
0.00-0.31 0.31-0.63 0.63-0.94 0.94-1.25 1.25-1.56
Mossong et al, 2008
1.56-1.88 1.88-2.19 2.19-2.50
10. Incidence of zoster
At what age
do individuals
get zoster?
Karhunen et al., 2009
11. A transmission model + zoster
Susceptible, (a,t) Infected, latent Infectious, VZV positive
S(a,t) phase L(a,t) I(a,t) with one
previous
exposure
(1-)v1(a,t)
(a,t)
Herpes zoster, h(a,d)
H(a,t)
VZV positive
with two
Vaccinated v2(a,t) previous
exposures
protected,
R(v)(a,t)
Removed, (a,t)
R(a,t)
VZV positive
with three
v1(a,t) previous
v2(a,t) exposures
etc.
Vaccinated Vaccinated Vaccinated
susceptible, latent, L(v)(a,t) infectious,
S(v)(a,t) (a,t) I(v)(a,t)
12. Effects of vaccination
Varicella transmission
stops in few years
Incidence of zoster
increases, in excess to
that due to aging
population
The extent of the
excess increase
depends on the model
assumptions
30-85% excess cases in
the next 50 years
13. Excess cases under 2 scenarios
Zoster immunity depends
solely on exposure to the virus
Zoster immunity depends
on exposure and aging
Karhunen et al., 2009
14. What happened next…
Cost-effective analysis
Varicella vaccination was deemed cost effective, even
under the worst case scenario for zoster
Vaccine-specific Expert Group (2008)
Recommendation, with ”consideration of potential
increase in zoster incidence” and a reference to potential
use of HZ vaccine
not necessarily safe for the (elderly) population
National Advisory Committee (2009)
No agreement: the decision was put on hold
15. Lessons learned
Worst-case scenarios should perhaps not present
the absolutely worst outcomes
The modelling group intended to maximise
certainty
However, the worst-case may have been taken as
a likely outcome
There was actually a wish to remove any reference
into zoster risk
Efficient communication of one’s own results
possible as long as one can participate in boards
Commitment to the implications of one’s own modelling
results is inevitable (and appropriate)
16. Human papillomavirus (HPV)
Common asymptomatic and usually transient
infection
Up to 30% of young adults are infected at any time
Infection may become persistent and progress to cancer
Cervical cancer (5.7/100,000 in Finland)
The incidence of disease is greatly modulated by the
very effective screening program in Finland
Vaccination protects against primary HPV
infection and (subsequent) disease
The impact of screening is intertwined with that of
vaccination
17. Introducing HPV vaccination?
The aims for dynamic modelling
To disentangle the underlying disease process from that
affected by the current screening program
To optimise the screening program
To consider the optimal introduction policy for HPV
vaccination
The model was constructed in two parts
(1) Transmission of the virus
(2) Progression of infection to disease
18. Elements of modelling HPV
TREATMENT AND MANAGEMENT
CIN0
Outcome CIN1 CIN2 CIN3 Ca
Screening testing testing testing testing testing/
sypmtoms
Rate of CIN0 CIN1 CIN2 CIN3 Cancer
infection
Clear Clear Clear Clear
Vänskä, Salo et al. 2012
19. The fate of HPV vaccination
(and screening)?
Vaccine-specific Expert Group and the National
Advisory Committee recommended introducing
the vaccine
The screening experts presented strong criticism
against the underlying analysis
Strong reliance on the current screening policy
The perception of the burden of disease was based on
the apparent incidence of disease
Opportunistic screening falls out of the sight of the
systematic screening program
The final decision was put on hold, primarily for
financial reasons
20. Lessons learned
Communicating modelling results to a group of
outside stakeholders in their own substance
matter area is extremely difficult
Without success in engaging the group from the first
beginning
Without the incentive originating from that group
Without expertise and tradition in the methods of
modelling in that group
If the model-based analysis is not totally
transparent, including its relation to
epidemiological data
Criticism is considered more acceptable
Criticism more likely misses the point
The justification of criticism is impossible to assess by
the third parties
21. Pneumococcus (Streptococcus pneumoniae)
Causes different forms of disease
Mild infections of the respiratory tract
Pneumonia
Meningitis
Is usually carried asymptomatically
New vaccines protect against disease due 10 or
13 types out of the >90 types
Vaccination affects asymptomatic carriage as well
This may lead to increase in carriage and disease
caused by the non-vaccine types
22. Setting the tender criteria
Currently, the 10-valent vaccine is in the national
immunisation program
A new tender process was to be prepared to
choose between the 10- and 13-valent vaccines
Price and quality (i.e. number of types)
Questions for modelling:
Considering the expected greater health benefits
from the 13-valent vaccine, how much more are
we prepared to pay for that?
What is the expected difference in the health
outcomes (incidence of disease)?
25. What happened next?
The Ministry accepted the tender criteria, based
on the modelling results
This was based on a simplified model of vaccine efficacy
against individual types
This fact was overlooked by the board, probably due to
too much preoccupance to other assumptions
The tender criteria have already been criticised
by the other vaccine provider
Criticism of the models not being truthful enough!
26. Lessons learned
Although the models incorporate a large number
of assumptions, only some of them usually catch
attention in expert panels
The communication needs to be based on few key
assumptions
It is not worthwhile to present solutions to problems,
which the expert panel does not know to appreciate in
the first hand
Implications of the decisions need to be made
explicit
27. Concluding remarks
Communication for public health decision makers
and science audiences differ
More emphasis on ”certainty” in public health
Peer-reviewed publications from the group give
more support and credibility
The modeller’s view may sometimes be
(appropriately) naive
We live in the world of models and methods!