1. Visiting Researcher, University of the Witwatersrand
Sex, risk and preferences: Multipurpose HIV prevention products in South Africa
Matthew Quaife
Research Fellow in Health Economics, London School of Hygiene and Tropical Medicine
Visiting Researcher, University of the Witwatersrand
STRIVE Learning Lab
30th November 2017
Collaborators and co-authors: Fern Terris-Prestholt, Robyn Eakle, Maria Cabrera, Sinead Delany-Moretlwe, Peter Vickerman

2. Background and motivation
South Africa has one of the largest and high profile generalised HIV epidemics in the world
Estimated 12% prevalence and increasing

3. Background and motivation
South Africa has one of the largest and high profile generalised HIV epidemics in the world
Estimated 12% prevalence and increasing
Predominantly heterosexual epidemic – has some nuances:
Women 1.4x more like to be HIV positive than men
Adolescent girls 8x more likely to be HIV positive than boys of the same age
HIV prevalence for female sex workers (FSWs) in South Africa estimated at 70% (in Johannesburg)

4. Background and motivation
South Africa has one of the largest and high profile generalised HIV epidemics in the world
Estimated 12% prevalence and increasing
Predominantly heterosexual epidemic – has some nuances:
Women 1.4x more like to be HIV positive than men
Adolescent girls 8x more likely to be HIV positive than boys of the same age
HIV prevalence for female sex workers (FSWs) in South Africa estimated at 70% (in Johannesburg)
For years, condoms were the only efficacious “product” to prevent HIV transmission
Many reasons why condoms have not been effective at preventing a large epidemic
E.g. gender norms, power asymmetry, transactional sex, incentives for risk in sex work

5. Background and motivation
New antiretroviral (ARV)-based HIV prevention methods on the brink of roll-out.
Five products in development – different ways of delivering ARV drugs
Potential to increase agency of vulnerable groups – no partner participation required

6. Background and motivation
New antiretroviral (ARV)-based HIV prevention methods on the brink of roll-out.
Five products in development – different ways of delivering ARV drugs
Potential to increase agency of vulnerable groups – no partner participation required
But:
Only oral PrEP and intravaginal ring have been proven efficacious
Single purpose – only protect against HIV (for the moment)
Concerns of substitution from condom use
Efficacy ≠ effectiveness => adherence issues

7. Background and motivation: Models

8. Background and motivation: Models
“13% of current HIV funding was found not to support priority interventions[…]
[This] should be de-prioritised, with funding reallocated to more evidence-based approaches.”
South African National Strategic Plan for HIV and TB: NDoH 2016.

9. Methods: Discrete Choice Experiment (DCE)

10. Methods: Discrete Choice Experiment (DCE)

11. Methods: Data Collection

12. Methods: Data Collection
Adult Females
Adult Males
Adolescent Females
Female sex workers
Total
203 recruited
202 recruited
204 recruited
203 recruited
812 recruited
35 self-reported HIV positive (17%)
16 self-reported HIV positive (8%)
5 self-reported HIV positive (2%)
81 self-reported HIV positive (40%)
137 self-reported HIV positive (17%)
10 not sexually active
4 not sexually active
126 not sexually active
0 not sexually active
140 not sexually active
158 completed DCE
182 completed DCE
73 completed DCE
122 completed DCE
535 completed DCE

13. Results: Product Preferences

14. Results: Product Preferences

15. Impact: Rollout scenarios
 Product(s)
HIV protection
Pregnancy protection
Scenario 1 
Oral PrEP X
Scenario 2
Intravaginal ring
Scenario 3
Scenario 4
Injectable ARV
Microbicide Gel
SILCS diaphragm & microbicide gel
Scenario 5
Diaphragm & microbicide gel
1. Current practice
2 & 3: Next few years
4. Kitchen sink
5. Multipurpose kitchen sink

16. Uptake Predictions

17. Impact: Model
Simple static transmission model using South African demographic and HIV epidemiological data
For each product (𝑥), protection is a function of efficacy ( 𝐸 𝑥 ) and use ( 𝑈 𝑥 )
𝑃 𝑥 = 𝐸 𝑥 𝑈 𝑥

18. Impact: Model
Simple static transmission model using South African demographic and HIV epidemiological data
For each product (𝑥), protection is a function of efficacy ( 𝐸 𝑥 ) and use ( 𝑈 𝑥 )
Then:
𝑃 𝑥 = 𝐸 𝑥 𝑈 𝑥
Overall protection = additional protection from new products – condom migration + existing condom protection
𝑃 𝑛 = 𝑈 𝑥 1− 1−𝜀 𝑖=1..𝑛 𝑈𝑐 𝑖 𝐸 𝑥 + 1−𝜀 𝑖=1..𝑛 𝐸 𝑖 𝑈𝑐 𝑖 +𝜀 𝑖=1..𝑛 1− 𝐸 𝑥 𝐸 𝑖 𝑈𝑐 𝑖 + 1− 𝑈 𝑥 𝑖=1..𝑛 𝐸 𝑖 𝑈𝑛𝑐 𝑖 𝑖=1..𝑛 𝐸 𝑖 𝑈𝑛𝑐 𝑖
(1−𝜀) = propensity to still use condoms, Uc and Unc = product use among condom/non-condom users, Ei = efficacy

19. Impact: DALYs averted
Estimate benefits from one year of product introduction
No consideration of staged uptake over time, adherence
DALYs averted through preventing HIV infections
Do not consider benefits from unintended pregnancies averted
Averaged DALYs averted per infection estimated for each population
Estimate model with low/medium/high HIV incidence for each group
No age-weighting
Discount rate 3% (all costs and benefits)
Willingness-to-pay threshold of $1,175 (Woods et al. 2016)

20. Cost model Fixed costs National start-up costs Training of providers
Mass media
MPT research and development
Variable costs
Facility distribution costs
Staff time
Product
Health system mark-up and overheads
Averted health costs
ART treatment
Planned and unplanned miscarriage and births

21. Cost-effectiveness

22. But PrEP is already here…
Women 16-24
Women 25-49
FSW
Incidence assumption
Low
Central
High
Single-purpose
Adding vaginal ring to PrEP (Scenario 2 compared to Scenario 1)
$1,691
$801
$30
$4,763
$3,282
$1,008
$792
$-66
$-398
Multi-purpose
Adding MPT ring to PrEP (Scenario 3 compared to Scenario 1)
$727
$243
$-225
$-401
$-482
$-669
$-532
$-709
$-791
Adding MPT range to single-purpose range (Scenario 5 compared to Scenario 4)
$1,214
$543
$-79
$88
$-114
$-503
$-1,810
$-1,502
$-1,334
*Negative ICER values in this table indicate cost-saving interventions with a positive impact

23. Conclusions
MPTs likely cost-effective among younger women (16-24) and FSWs
The most cost-effective scenarios were those with MPT products
Likely cost-effective to add a MPT ring to PrEP provision, other scenarios more nuanced
Estimates very sensitive to incidence
Overall impact likely to be low
Full scenario predicts 19% incidence reduction among younger women, 8% among older women and FSWs
UNAIDS targets estimated to lead to 48% reduction in incidence

24. Acknowledgements All study participants
Interviewers and staff of Progressus Research and Development
Bill and Melinda Gates Foundation
Economic and Social Research Council

25. Thank you for listening
@matthew_quaife

26. Additional slides

27. Uptake Predictions
DCEs tell us how much people value different attributes -
E.g. Pregnancy protection is twice as important as STI protection
Cardinal estimates of utility provided by attributes
Adult Females
Adolescent Girls
FSW
HIV protection (full)
2.33 (0.53)***
2.59 (0.88)***
2.19 (0.425)***
Pregnancy prevention
0.16 (0.05)***
0.48 (0.09)***
0.14 (0.044)***
STI protection
0.22 (0.06)***
0.44 (0.1)***
0.36 (0.048)***

28. Contraceptive protection (varied)
Uptake Predictions
DCEs tell us how much people value different attributes
E.g. Pregnancy protection is twice as important as STI protection
We know the likely attributes of new products. E.g.:
Product
HIV efficacy
STI efficacy
Contraceptive protection (varied)
Frequency of use
Oral PrEP 61 N
N (Y)
Daily
Vaginal Ring 55
Weekly

29. Contraceptive protection (varied)
Uptake Predictions
DCEs tell us how much people value different attributes
E.g. Pregnancy protection is twice as important as STI protection
We know the likely attributes of new products. E.g.:
Because we know how much people value each attribute, we can predict the probability that somebody will choose oral PrEP over a vaginal ring
Product
HIV efficacy
STI efficacy
Contraceptive protection (varied)
Frequency of use
Oral PrEP 61 N
N (Y)
Daily
Vaginal Ring 55
Weekly
𝑃𝑟𝑜𝑏𝑎𝑏𝑖𝑙𝑖𝑡𝑦 𝑜𝑟𝑎𝑙 𝑃𝑟𝐸𝑃 = 𝑢𝑡𝑖𝑙𝑖𝑡 𝑦 𝑜𝑟𝑎𝑙 𝑃𝑟𝐸𝑃 𝑢𝑡𝑖𝑙𝑖𝑡 𝑦 𝑜𝑟𝑎𝑙 𝑃𝑟𝐸𝑃 +𝑢𝑡𝑖𝑙𝑖𝑡 𝑦 𝑣𝑎𝑔𝑖𝑛𝑎𝑙 𝑟𝑖𝑛𝑔

30. The economics of sex work

31. Hypothesis Price premium of unprotected sex Supply1: Baseline
Supply2: After intervention A
Price decrease B
Demand: remains constant
Quantity increase
Quantity of unprotected Sex

32. Methods: The Choice Experiment

33. Methods: Framing
Introduction and survey questions
First CE task (no framing)
“You have the choice between providing services to one of two clients. Which would you prefer?”

34. Methods: Framing Introduction and survey questions
First CE task (no framing)
Introduction to PrEP

35. Methods: Framing HIV –ves only Introduction and survey questions
First CE task (no framing)
Introduction to PrEP
Second CE task (with framing)
“Now I would like you to choose between 10 more sets of clients, but this time I would like you to make your choices imagining you were using a product which prevented you from getting infected with HIV. This means that there would be no risk of getting HIV from any client, whether or not you use a condom.”

36. MNL Results (1) Unframed MNL Coeff. SE Price (ZAR 100) 0.16 *** 0.56
Condom
8.04
0.32
Anal sex
-4.99
0.24
Think client has HIV
-0.78
0.19
Think client has STI
-1.38
0.21
Opt-out
2.90
0.215
Interaction terms
PrEP framing x price
PrEP framing x condom use
PrEP framing x anal sex
PrEP framing x client HIV
PrEP framing x client STI
PrEP framing x opt-out
Log likelihood
-1083
Implied condom differential
ZAR 4,903
Reduction of 73%
*p<0.1, **p<0.05, ***p<0.01

37. MNL Results (1) (2) Unframed MNL PrEP framed MNL Coeff. SE
Price (ZAR 100)
0.16
***
0.56
0.24
0.05
Condom
8.04
0.32
6.56
0.29
Anal sex
-4.99
-5.01
0.23
Think client has HIV
-0.78
0.19
-0.46
0.18
Think client has STI
-1.38
0.21
-1.09
Opt-out
2.90
0.215
1.83
Interaction terms
PrEP framing x price
PrEP framing x condom use
PrEP framing x anal sex
PrEP framing x client HIV
PrEP framing x client STI
PrEP framing x opt-out
Log likelihood
-1083
-1273
Implied condom differential
ZAR 4,903
ZAR 2,733
Reduction of 73%
*p<0.1, **p<0.05, ***p<0.01

38. MNL Results (1) (2) (3) Unframed MNL PrEP framed MNL Interacted MNL
Coeff. SE
Price (ZAR 100)
0.16
***
0.56
0.24
0.05
0.14
0.48
Condom
8.04
0.32
6.56
0.29
7.53
0.26
Anal sex
-4.99
-5.01
0.23
-4.95
0.22
Think client has HIV
-0.78
0.19
-0.46
0.18
0.87
0.17
Think client has STI
-1.38
0.21
-1.09
-1.31
Opt-out
2.90
0.215
1.83
2.58
0.15
Interaction terms
PrEP framing x price
0.12 **
PrEP framing x condom use
-0.40
PrEP framing x anal sex
-0.17
PrEP framing x client HIV
0.50
0.10
PrEP framing x client STI
0.92
PrEP framing x opt-out
-0.48
0.11
Log likelihood
-1083
-1273
-2386
Implied condom differential
ZAR 4,903
ZAR 2,733
Reduction of 73%
*p<0.1, **p<0.05, ***p<0.01