Measles Strategic Planning Tool: Analysis of MCV strategies in developing countries. Emily Simons 29 January 2009

Transcription

1 Measles Strategic Planning Tool: Analysis of MCV strategies in developing countries Emily Simons 29 January 2009

2 Overview The MSP tool Results by question For Indian states: what is best strategy to accelerate disease control and does the optimal strategy change as MCV1 coverage increases? For African countries and Cambodia: how much do countries benefit from MCV2 and do the benefits vary as MCV1 coverage increases? For Latin American countries: At what MCV1 and MCV2 coverage rates can SIAs be removed without substantial risk of outbreaks? General conclusions 2

3 The MSP Tool User-defined scenarios: change coverage, introduce MCV2 or SIAs Quasi-dynamic state model that predicts potential measles cases, DALYs, deaths, and costs Historical ( ) time series data, including coverage, SIAs, reported cases, schedules, and population estimates ( ) Global parameters: vaccine efficacy, CFR age multiplier, discount rate, herd immunity threshold, initial value of infectiousness Country specific parameters: costs per dose, CFR Cohort specific characteristics: proportion immune, FOI, cases 3

4 The MSP Tool Vaccine failure, susceptible Protected by maternal AB MCV1 Immune Birth cohort Susceptibles at 12 months 1 year old cohort, X% immune Background mortality Deaths Cases Recover, immune 4

5 Basic calculation Based on series of algebraic equations that determine % susceptible of each birth cohort and annual # cases FOI adjusted according to proportion of population immune (greater immunity, lower FOI) Distribution curve of FOI vs. % of cohort immune fit through MLE 100* S ( t) of observed data A log(100* S( t)) A F( t) = Fi Herd immunity threshold=10.5% log( H ) Abrupt shift in transmission as % immune 89.5% FOI cohort specific: more dynamic than Miller/Rabaa, less dynamic than Burgess/Levin 5

6 Assumptions & limitations Assumptions Homogeneous vaccination coverage across country Homogeneous mixing No difference in cost of MCV2 in 2 nd year of life and at school-entry Limitations Time period= Will not capture large outbreaks around or near 2025, big changes to MCV activities can take 10 years to equilibrate Incidence: over-estimated, MSP only includes population 0-69 years old Tends to over estimate incidence when coverage high and underestimate size of outbreaks when coverage low SIAs performed once every 3 years for DRC (not rolling) 6

7 Indian scenarios

8 Annual incidence per 100, , Indian scenarios MCV1 coverage Annual incidence per 100,000 total population, Baseline S1 (incr MCV1) S2 (18M MCV2) Bihar Maharastra Orissa S3 (SIAs) Karnataka Tamil Nadu 46% 74% 86% 90% 95% 8

9 Percent reduction in incidence over baseline , Indian scenarios 100% 90% Percent reduction in incidence, % 70% 60% 50% 40% 30% 20% 10% MCV1 coverage 0% 46% Bihar Maharastra 74% Orissa 86% Karnataka 90% Tamil Nadu 95% S3 (SIAs) S2 (18M MCV2) S1 (incr MCV1) 9

10 Cost-effectiveness: India (2008 USD) Cost per dose delivered (no sub-national variation): $2.01 via routine system $0.45 via SIA State Total increase in costs over baseline, S1 (Incr MCV1) S2 (18M MCV2) S3 (SIAs) S1 (Incr MCV1) Incremental cost effectiveness ratios per case averted S2 (18 M MCV2) S3 (SIAs) Bihar $16,937,715 $34,099,136 $44,056,617 $1.78 $9.20 $2.00 Maharashtra $5,337,593 $45,133,068 $27,472,204 $1.96 $12.21 $2.63 Orissa $122,119 $19,161,285 $9,064,095 $0.49 $14.15 $3.16 Karntaka N/A $26,424,866 $13,443,472 N/A $15.40 $3.86 Tamil Nadu N/A $27,201,943 $13,062,387 N/A $17.58 $

11 Increase in cost per additional case averted compared to baseline, Indian scenarios $18 $16 Cost per additional case averted, 2008 USD $14 $12 $10 $8 $6 $4 $2 MCV1 coverage $0 46% 74% Bihar Maharastra Orissa 86% Karnataka 90% Tamil Nadu 95% S2 (18M MCV2) S3 (SIAs) S1 (incr MCV1) 11

12 Conclusions: single routine dose states All strategies are cost-effective Increasing MCV1 extremely cost effective when MCV1 coverage <90% SIAs more effective than MCV2 12

13 Africa + Cambodia scenarios

14 Annual measles cases per 100,000 AFRO/WPRO scenarios, Average annual incidence per 100, MCV1 coverage 0.0 Eq. Guinea 51% 73% DRC Cameroon 73% Cambodia 79% Ghana 85% Rwanda 95% Baseline S2 (MCV2 7Y) S1 (MCV2 18 M) 14

15 Percent reduction in cases over baseline 100% AFRO/WPRO Percent reduction in incidence over baseline 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% MCV1 coverage Eq. Guinea DRC Cameroon Cambodia Ghana Rwanda 51% 73% 73% 79% 85% 95% S2 (MCV2 7Y) S1 (MCV2 18 M) 15

16 AFRO/WPRO Costs Cost per vaccinated child (2008 USD) Country Eq. Guinea Cameroon DRC Cambodia Ghana Dose via routine system* $6.39 $4.24 $3.07 $2.12 $1.50 Dose via SIA $0.92 $0.63 $0.91 $0.63 $0.78 Rwanda $2.01 $0.80 *No distinction in costs between first and second routine doses 16

17 Cost-effectiveness of AFRO/WPRO scenarios (2008 USD) Country Eq. Guinea Cameroon DRC Cambodia Ghana Rwanda Total increase in costs over baseline, S1 or S2* $848,099 $18,967,055 $81,608,127 $10,093,759 $11,077,741 $9,479,794 Incremental cost effectiveness ratios per case averted S1 (MCV2 18M) $191 $233 $146 $170 $163 $333 S2 (MCV2 7Y) $194 $464 $314 $377 $240 $646 per DALY averted S1 (MCV2 18M) $120 $164 $79 $132 $103 $263 S2 (MCV2 7Y) $158 $362 $189 $355 $164 $542 *No distinction in costs between first and second routine doses. 17

18 Conclusions: Africa/Cambodia All second opportunities have similar impact Use of MCV2 supported by both effectiveness and cost data in continued presence of SIAs MCV2 at 18 months can reduce incidence by 45-85% when MCV1 73% MCV2 more effective at 18M than school age even though fewer previously unvaccinated children reached 18

19 AMRO scenarios

20 Predicted cases per 1,000, , AMRO scenarios 70 Average annual incidence per 1,000, MCV1 coverage MCV2 coverage SIA coverage Paraguay Costa Rica Mexico El Salvador S1 (No SIAs) Baseline 20

21 AMRO Costs Cost per child (2008 USD) Country Paraguay Costa Rica Mexico El Salvador Dose via routine system* $15.87 $82.37 $82.37 $6.87 Dose via SIA $0.93 $5.81 $5.81 $0.93 *No distinction in costs between first and second routine doses 21

22 Cost-effectiveness of AMRO scenarios Country Paraguay Costa Rica Mexico El Salvador Cost saved by removing SIAs* (2008 USD) Total, $2,592,967 $6,359,986 $237,250,964 $2,636,314 per additional case $26 $164 $1,041 $5,091 per additional DALY $98,033 $38,806 $227,987 $518 *Difference in costs are not entirely savings. Expenditures include sunk costs that are not recoverable, such as training and capital, and costs shared with integrated services that are also not recoverable. 22

23 Conclusions: two routine dose countries Supports PAHO benchmark of ~ 95% coverage for MCV1 prior to removal of SIAs 90-95% range of MCV1 needs further assessment MCV2 coverage <95% combined with 95% MCV1 may sustain elimination, but further assessment needed 23

24 Summary 1. India: what is best strategy to accelerate disease control and does the optimal strategy change as MCV1 coverage increases? Increasing MCV1 extremely cost effective when MCV1 coverage <90% SIAs have greater impact than MCV2 across all MCV1 coverage 2. Africa/Cambodia: how much do countries benefit from MCV2 and do the benefits vary as MCV1 coverage increases? MCV2 at 18 months can reduce incidence by 45-85% when MCV1 73% MCV2 at 18 months more effective than MCV2 at 7 years, despite low number of zero-dose children reached at 18 months MCV2 becomes more effective at higher MCV1 coverage levels 3. Latin America: At what MCV1 and MCV2 coverage rates can SIAs be removed without substantial risk of outbreaks? ~ 95% MCV1 coverage for prior to reduction of SIAs Range of MCV2 coverage with 95% MCV1 needs further assessment 24

25 Acknowledgements Tracey Goodman, Peter Strebel, Alya Dabbagh Lara Wolfson 25

26 Questions? 26