1. 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
Preliminary results, working on another version of the model.
I will present a model we are working on. A model is an abstraction of reality and cannot incorporate all epidemiological or economic factors. We have to be a little creative when looking at models because they cannot incorporate all features: they are designed to capture some portion of reality and simplify it so we can help understand the process and make an informed decision. Models do not represent reality exactly (because models cannot completely represent reality). Pertussis is a very difficult and complicated disease, epidemiologically.
A good model captures enough of reality to identify differences in strategies or epidemiological factors, but abstracts from reality to make the model usable and understandable.
The decision model I present is meant to help make an informed decision – it is not designed to make the decision for the person who uses it.

2. Background Bordetella pertussis – “whooping cough” WHO statistics
152,535 cases (2007)
US National Statistics
25,827(2004)
25,626 (2005)
15,632 (2006)
McNabb et al. Centers for Disease Control and Prevention. Summary of notifiable diseases – United States, MMWR Morb Mortal Wkly Rep 2008; 55:53.
5/18/2018 2

3. Adapted from McNabb et al. Centers for Disease Control and Prevention
Adapted from McNabb et al. Centers for Disease Control and Prevention. Summary of notifiable diseases – United States, MMWR Morb Mortal Wkly Rep 2008; 55:53.
5/18/2018

4. Adapted from McNabb et al. Centers for Disease Control and Prevention
Adapted from McNabb et al. Centers for Disease Control and Prevention. Summary of notifiable diseases – United States, MMWR Morb Mortal Wkly Rep 2008; 55:53.
5/18/2018 4

5. 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.

6. 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.

7. Outbreak in Douglas County, NE

8. 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)

9. One School Based Outbreak (24 Pertussis Cases)
Activity
Total
Per Case
Hours
1,003.5
41.81
Extra/ compensation hours 28
1.17
Phone calls
507
21.13
Miles traveled 97
4.04
# contacts recommended chemoprophylaxis
148
6.17
Cost w/ overhead (2008)
$51,327
$2,138
5/18/2018

10. 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.

11. Close contacts of infants
All close contacts
Close contacts of infants
adult
pertussis case

12. Method Decision / cost effectiveness analysis
Very little data – quantify uncertainty
Incorporate epidemiological and economic factors
TreeAge software
From the health department perspective

13. Assumptions Data driven Observational 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

14. Decision for Close Contacts of a Case

15. All Close Contacts
next to infant
Depends on branches, natural transmission rate, vaccine efficacy, chemoprophylaxis efficacy| early
pertussis
vaccinated
early
diagnosis
(< 1wk)
no false
“+”
all close
contacts
False positive can also represent miss-diagnosis.

16. Close Contacts of Infants
next to
infant
no false “+”
close contacts of
infants
not next to
infant

17. Quiz. : There is an outbreak of pertussis at a local school
*Quiz*: There is an outbreak of pertussis at a local school. What is the best strategy?
Hide under desk and call your mother!
Call in sick.
It depends!
Do we want to prevent pertussis cases or infant cases?
How many hours/ resources are available?
The first choice is my personal favorite, I do this quite frequently. You can include significant others in choice A as well. How many other people like to do this? I tell my mom, more pertussis cases, more phone calls – she likes pertussis.

18. Estimated Infant Cases
95% Vaccine Uptake
Intervention
Estimated Adult Cases
Estimated Infant Cases
EstimatedCost($)1
All close contacts
Least
.0859
178,794
Close contacts of infants
Middle
107,730
Monitor & treat case
Most
.134
42,508
** “all close contacts” is more expensive, but has the same estimated number of infant cases as “close contacts of infants.”
1All cost figures are in December 2008 dollars. Preliminary data, results subject
to change.

19. Comparing Strategies Cost per additional case averted
Cost per additional case averted of strategy (i) relative to the TREAT strategy.
Cost per additional
case averted

20. 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.

21. 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.

22. 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

23. Pertussis Outbreak Tool
*Note: Preliminary demonstration data, not for analysis or use.

24. 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

25. Acknowledgements CDC Douglas County HD, Omaha, NE Oregon State HD
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

26. Contact Information
Garrett R. Beeler Asay
Health Services Research and Evaluation Branch
Immunization Services Division
hrp9(AT)cdc.gov
Thank you!
5/18/2018

27. Appendix Slides

28. Global Values Variable Base Best Worst Dist. P(infant) .036 .2 .01
Triangular
P(false “+”)
0.2
0.1
0.5
Uniform
P(vaccinated)
0.95
0.9
Vaccine efficacy
0.8
P(early diagnosis)
0.4
Prophylaxis efficacy| early diagnosis
Prophylaxis efficacy| late diagnosis
0.3
Cost of false positive
410
200
600

29. Local Values All close contacts Base Best Worst Dist. Cost / case1
2,117
371
5,096
Triangular
Prophylaxis compliance rate .5 .9
Uniform
Close contacts of infants
Cost / case
529.25
1,587.75
P(infant pertussis | close contacts of infants) 1
0.7
Treat individual
410.1
205.03
615.09
1 Beeler Asay et al. (2009), Lindahl & Poissant (2005), and Calugar et al. (2006).