UNIVAC decision support model A universal framework for evaluating vaccine policy options in low- and middle-income countries

Transcription

1 UNIVAC decision support model A universal framework for evaluating vaccine policy options in low- and middle-income countries Andrew Clark, London School of Hygiene and Tropical Medicine

2 Key questions 1. How do you access, navigate and run UNIVAC? 2. How are the UNIVAC inputs used to generate outputs?

3 Key questions 1. How do you access, navigate and run UNIVAC? 2. How are the UNIVAC inputs used to generate outputs?

4 Key questions 1. How do you access, navigate and run UNIVAC? 2. How are the UNIVAC inputs used to generate outputs?

5 Main output (outcome measure) 1. Cost-utility ratio Cost per DALY averted

6 Outputs of UNIVAC 1. Cost-utility ratio Cost per DALY averted 2. Vaccine costs Incremental vaccine costs 3. Healthcare costs Healthcare costs averted 4. Disease events Cases, visits, hosps., deaths, DALYs 5. Adverse events Cases, visits, hosps., deaths, DALYs 6. Benefit-risk ratio e.g. Deaths averted per death caused

7 Without vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by using United Nations Population Division (UNPOP) projections of the number of individuals that will be alive in each single year of age (and single calendar year) as the birth cohort ages

8 BIRTH COHORTS CALENDAR YEARS

9 BIRTH COHORTS Population, no vaccine CALENDAR YEARS etc... Years of age 9

10 Without vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by using United Nations Population Division (UNPOP) projections of the number of individuals that will be alive in each single year of age (and single calendar year) as the birth cohort ages Multiply by age-specific rates of disease per 100,000 per year to estimate numbers of disease events

11 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS etc... Years of age 11

12 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Years of age For simplicity, this example focuses on disease in under-fives 12

13 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Years of age 13

14 Without vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by using United Nations Population Division (UNPOP) projections of the number of individuals that will be alive in each single year of age (and single calendar year) as the birth cohort ages Multiply by age-specific rates of disease per 100,000 per year to estimate numbers of disease events If you want to account for changes in inputs over time (e.g. demography, mortality rates, coverage, price) then repeat for up to 30 birth cohorts

15 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Years of age 15

16 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS

17 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS

18 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS

19 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS

20 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS

21 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Also useful if you want to report results by calendar year

22 Without vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by using United Nations Population Division (UNPOP) projections of the number of individuals that will be alive in each single year of age (and single calendar year) as the birth cohort ages Multiply by age-specific rates of disease per 100,000 per year to estimate numbers of disease events If you want to account for changes in inputs over time (e.g. demography, mortality rates, coverage, price) then repeat for up to 30 birth cohorts Repeat for each disease type and outcome

23 Disease type 1 Cases Visits Hosps. Deaths

24 Cases Visits Hosps. Deaths Disease type 1 Disease type 2

25 Cases Visits Hosps. Deaths Disease type 1 Disease type 2 Disease type 3 up to 10 types

26 Example: Rotavirus configuration 1 Cases Visits Hosps. Deaths Any RVGE

27 Example: Rotavirus configuration 2 Cases Visits Hosps. Deaths Any RVGE

28 Example: Rotavirus configuration 3 Cases Visits Hosps. Deaths Any GE

29 Example: Rotavirus configuration 4 Cases Visits Hosps. Deaths Non-severe RVGE Severe RVGE

30 Example: Rotavirus configuration 5 Cases Visits Hosps. Deaths Non-severe RVGE Severe RVGE Intussusception The background rate of severe adverse events can also be included if required. Users can then enter the relative risk of vaccination compared to this background rate to estimate vaccine-related events.

31 With vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by specifying the period of vaccination

32 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Vaccinate infants born

33 With vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by specifying the period of vaccination Multiply age-specific disease events by: 1 [ (% covered by only 1 dose x efficacy of dose 1) + (% covered by only 2 doses x efficacy of dose 2) + (% covered by only 3 doses x efficacy of dose 3).etc. ]

34 With vaccination, how many disease events can we expect over the lifetime of a birth cohort? Start by specifying the period of vaccination Multiply age-specific disease events by: 1 [ (% covered by only 1 dose x efficacy of dose 1) + (% covered by only 2 doses x efficacy of dose 2) + (% covered by only 3 doses x efficacy of dose 3).etc. ] This calculation is applied by year of age 5-99 years and by week of age <5 years. UNIVAC therefore asks for additional inputs <5yrs: Age distribution of disease by week of age <5yrs; Vaccine coverage/timeliness by week of age <5yrs; Vaccine efficacy by time in weeks since dose given.

35 BIRTH COHORTS Deaths, no vaccine CALENDAR YEARS Vaccinate infants born

36 BIRTH COHORTS Deaths, routine vaccine CALENDAR YEARS Vaccinate infants born

37 BIRTH COHORTS Deaths, routine vaccine CALENDAR YEARS Vaccinate infants born - and track future benefits

38 COMPARATOR deaths without vaccine NEW OPTION 590 deaths with vaccine e.g. ~50000 future deaths prevented if all children born - are tracked over their lifetimes

39 UNIVAC advantages and drawbacks Advantages Accessibility developed in Excel so familiar to most users; Transparency can be easily explained to national teams and decision makers; Simplicity uses a minimal set of inputs and steps; Flexibility can be quickly adapted to evaluate new options in a timely way; Comparability allows for more standardised comparisons between vaccine policy options; Drawback Static unlike dynamic models, UNIVAC does NOT track the number of susceptible, infectious and immune individuals over time, so cannot directly simulate herd (and other indirect) effects. However, in mitigation (!), calibration of dynamic models: can be a lengthy/complex process; may not provide estimates defensible by MoH if based on poor quality data; may not be necessary if plausible whatif scenarios can demonstrate that inclusion of indirect effects would not change the recommendation/decision.

40 If you want to know more about The PAHO/WHO Provac Initiative The Provac Toolkit Partners