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A decision analysis of pertussis
control measures
April 1st, 2009
Garrett R. Beeler Asay, Ph.D.
Immunization Services Division
Collaborative work w/
Division of Bacterial Diseases
Centers for Disease Control and Prevention
Background
• Bordetella pertussis – “whooping cough”
• WHO statistics
– 152,535 cases (2007)
• US National Statistics
– 25,827(2004)
– 25,626 (2005)
– 15,632 (2006)
5/7/2017
McNabb et al. Centers for Disease Control and Prevention. Summary of notifiable
diseases – United States, 2006. MMWR Morb Mortal Wkly Rep 2008; 55:53.
2
Adapted from McNabb et al. Centers for Disease Control and
Prevention. Summary of notifiable diseases – United States, 2006.
MMWR Morb Mortal Wkly Rep 2008; 55:53.
5/7/2017
3
5/7/2017
Adapted from McNabb et al. Centers for Disease Control and
Prevention. Summary of notifiable diseases – United States,
2006. MMWR Morb Mortal Wkly Rep 2008; 55:53.
4
Pertussis Diagnosis &
Transmission
– whoop not always present, cold-like
symptoms
– not suspected until prolonged cough
– cases can build up large numbers of contacts
(80% attack rate in households1)
1Centers for Disease Control and Prevention. Epidemiology and Prevention of
Vaccine-Preventable Diseases. Atkinson W, Hamborsky J, McIntyre L, Wolfe S, eds.
10th ed. Washinton DC: Public Health Foundation, 2007.
Pertussis Control Measures
• Treat case
• Trace close contacts, recommend
chemoprophylaxis & vaccinate if eligible
• Test, monitor for signs of cough
Source: Adapted from Committee on Infectious Diseases, Red Book: 2006 Report of the
Committee on Infectious Diseases, 27th Edition, 2006 and Guidelines for the Control of
Pertussis Outbreaks, NIP, CDC, 2000.
Outbreak in Douglas County, NE
Outbreak Characteristics
• School based
• Suburb of Omaha, Nebraska
• Total population 1000
– Students, staff, parents, siblings
• 36 infants1 (< 1 year old)
• Vaccine uptake high (~95%)
• 24 pertussis cases
1Thomas,
Cynthia, CDC working paper (2009)
One School Based Outbreak
(24 Pertussis Cases)
Activity
Hours
Total
Per Case
1,003.5
41.81
Extra/ compensation
hours
Phone calls
28
1.17
507
21.13
Miles traveled
97
4.04
# contacts recommended
chemoprophylaxis
Cost w/ overhead (2008)
148
6.17
$51,327
$2,138
5/7/2017
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Research Question
• Can we reduce costs by changing control
measures/ protocols?
– Oregon HD recommends chemoprophylaxis
high risk contacts only
– Report
• substantial reductions in time spent on control of
pertussis
• better at identifying those who are most “at-risk”
Source: Liko, Juventila and Paul Lewis (2008). Oregon Pertussis Guidelines:
Before and After, National Immunization Conference presentation slides.
All close contacts
adult
pertussis
case
Close contacts of infants
Method
• Decision / cost effectiveness analysis
– Very little data – quantify uncertainty
– Incorporate epidemiological and economic
factors
– TreeAge software
• From the health department perspective
Assumptions
• Data driven
– Attack rate in
households
– Cost of all close
contact strategy
– Vaccine uptake
– Vaccine efficacy
– Proportion of infants in
population
• Observational
– Chemoprophylaxis
compliance close contacts
of infants
– Efficacy of
chemoprophylaxis early
– Likelihood of early
diagnosis
– Cost per case close
contact of infants
– Cost per case treat
Decision for Close Contacts
of a Case
All Close Contacts
early
vaccinated
diagnosis
(< 1wk)
pertussis
next to infant
no false
“+”
all close
contacts
Depends on branches, natural transmission rate, vaccine
efficacy, chemoprophylaxis efficacy| early
Close Contacts of Infants
next to
infant
close
contacts
of
infants
no false
“+”
not next
to
infant
*Quiz*: There is an outbreak of
pertussis at a local school. What is
the best strategy?
A. Hide under desk and call your mother!
B. Call in sick.
C. It depends!
•
•
Do we want to prevent pertussis cases or
infant cases?
How many hours/ resources are
available?
95% Vaccine Uptake
Intervention
All close contacts
Close contacts of
infants
Monitor & treat
case
Estimated Adult
Cases
Estimated Estimated
Infant Cases Cost($)1
Least
Middle
.0859
.0859
178,794
107,730
Most
.134
42,508
1All
cost figures are in December 2008 dollars. Preliminary data, results subject
to change.
** “all close contacts” is more expensive, but has the
same estimated number of infant cases as “close
contacts of infants.”
Comparing Strategies
• Cost per additional case averted of strategy (i)
relative to the TREAT strategy.
Cost per additional
Cost i – Cost TREAT

case averted
Cases TREAT  Casesi
Cost per case averted relative to
TREAT (95% uptake)
Intervention
All Pertussis Cases
Infant Pertussis
Cases
Close contacts
of infants
$60,390
$1,346,308
All close
contacts
$6,641
$2,813,224
All cost figures are in December 2008 dollars. Preliminary data, results subject
to change.
Cost per case averted relative to
TREAT (20% uptake)
Intervention
All Pertussis Cases
Infant Pertussis
Cases
Close contacts
of infants
$46,736
$1,355,471
All close
contacts
$6,575
$5,153,099
All cost figures are in December 2008 dollars. Preliminary data, results subject
to change.
Limitations & Future Work
• More validation work on model
• Health department perspective
– Collecting more data on HD response costs
• No lab testing costs
• How many resources should a HD put into
pertussis?
• Developing a tool for HD departments
Pertussis Outbreak Tool
*Note: Preliminary demonstration data, not for analysis or use.
Preliminary Conclusions
• The best intervention strategy depends on
a HD’s goals
• When the aim is to protect infants and high
risk contacts, the all close contact strategy
is more expensive
Acknowledgements
• CDC
– Division of Bacterial Diseases: Tami Skoff & Jennifer
Liang, Tom Clark, Nancy Messonnier
– HSREB, Mark Messonnier, Bo Cho, Fangjun Zhou
– Division of HIV/ AIDS, Prabhu Vimalanand
– NCIRD, Ismael Ortega-Sanchez
• Douglas County HD, Omaha, NE
– Adi Pour, Carol Allensworth, Anne O’Keefe, Bonnie
Harmon, DCHD staff
• Oregon State HD
– Juventila Liko & Paul Cieslak
Contact Information
• Garrett R. Beeler Asay
– Health Services Research and Evaluation
Branch
– Immunization Services Division
– hrp9(AT)cdc.gov
• Thank you!
5/7/2017
26
Appendix Slides
Global Values
Variable
Base
Best
Worst
Dist.
P(infant)
P(false “+”)
P(vaccinated)
.036
0.2
0.95
.2
0.1
0.9
.01
0.5
0.1
Triangular
Uniform
Triangular
Vaccine efficacy
P(early diagnosis)
Prophylaxis efficacy|
early diagnosis
0.8
0.2
0.9
0.4
0.5
0
Triangular
Uniform
0.8
0.9
0.5
Uniform
0.3
0.5
0
Uniform
410
200
600
Uniform
Prophylaxis efficacy|
late diagnosis
Cost of false positive
Local Values
All close contacts
Base
Best
Worst
Dist.
Cost / case1
2,117
371
5,096
Triangular
.5
.9
0
Uniform
1058.50
529.25
P(infant pertussis | close
contacts of infants)
1
0.7
1
Uniform
Prophylaxis compliance
rate
.9
1
.5
Uniform
410.1
205.03
615.09
Triangular
Prophylaxis compliance
rate
Close contacts of infants
Cost / case
1,587.75 Triangular
Treat individual
Cost / case
1 Beeler
Asay et al. (2009), Lindahl & Poissant (2005), and Calugar et al. (2006).