1. World Health Organization
15 January 2019
WHO measles mortality estimates,
Emily Simons
Global Measles Management Meeting
17 March 2010

2. Overview Background Brief description of method Provisional results
Next steps

3. World Health Organization
Background
World Health Organization
15 January 2019
3 progressively more refined models of measles mortality since 2000 Stein 2003, Wolfson 2007, Ferrari 2011
2011 model addresses QUIVER recommendations to incorporate:
surveillance data
dynamic transmission
herd immunity
objective definition for countries that have highly reliable surveillance data
Country consultation: letters sent to 119 countries
Dynamic in sense that susceptible in year x affects susceptibles in year x+1, but does not have bells and whistles of highly complex dynamic models because this requires far more data, most of which is not routinely available, and added benefit of this level of complexity appears minimal (E.g. there is no person-to-person contact matrix or age structure or subnational heterogeneity in coverage.) Herd immunity component may need some adjustment pending feedback from country consultation process. Definition for countries where surveillance data is more reliable than model estimates: countries that have eliminated measles or are in lowest quintile of national child mortality rates

4. Overview of 2011 measles mortality estimation method
Annual country-specific cases estimated by method called state-space model
Cases distributed across age groups
Age, country, and year-specific CFRs applied to cases

5. State-space model
For each country independently, model compares two data for each year: a) reported cases and b) number of susceptibles based on susceptible-infected-recovered model
# of true cases estimated for year t, with random error added
Subtract these cases from susceptibles, repeat process for year t+1
1,000 iterations give distribution of most likely number of cases for time series

6. 15 January 2019

7. Age distribution 172,191 line-listed cases from 102 countries
Outcome: age group
Explanatory variables:
GBD Region
MCV1 coverage
Predicted age distribution of reported measles cases by MCV1 coverage level and region

8. Case fatality ratios
Age and country-specific CFRs from Wolfson IJE updated for new studies Nepal and India
Indexed to U5MR to reflect evidence of decline in deaths due to pneumonia, diarrhoea and malnutrition

9. Provisional global estimated measles mortality and reported cases
World Health Organization
15 January 2019
74% global mortality reduction over
79% reduction over according to Lancet

10. New model vs. Lancet model measles mortality estimates
79%
74%

11. Estimated measles deaths and reduction in mortality since 2000*
79%
87%
26%
82%
15 January 2019
*provisional

12. Estimated total measles deaths in 2000 and 2009
% mortality reduction
Lancet
New model
Region
2009
2000
93%
25602
385755
87%
52247
411631
AFR
91%
<100
99%
AMR
96%
4130
100008
79%
9540
46113
EMR
73%
157
585
667
EUR
48%
127817
244871
26%
88750
119618
SEAR
92%
1972
24701
82%
3876
21689
WPR
159679
755921
74%
154502
599721
Global

13. Next steps Respond to feedback from country consultation
Many supportive responses, but some feel the data do not reflect their reality
Will modify input data, may modify structural features like herd immunity
Key challenge: how to identify when surveillance sensitivity has changed?
Clearance: required to fit within estimates of overall declining child mortality and estimated declines in other causes of child mortality
Challenge: non-V.P. diseases do not have annual surveillance/coverage data  very different methods, with much greater lag time
Peer review

14. Back-up slides

15. Measles mortality estimates, African Region
87%
93%

16. Measles mortality estimates, Eastern Mediterranean Region
96%
79%

17. Measles mortality estimates, South-East Asia Region
48%
26%

18. Measles mortality estimates, Western Pacific Region
93%
82%