Incorporating end-users' voices into the development of an implant for HIV prevention: a discrete choice experiment in South Africa and Zimbabwe

Abstract

Background: Input from end-users during preclinical phases can support market fit for new HIV prevention technologies. With several long-acting pre-exposure prophylaxis (PrEP) implants in development, we aimed to understand young women's preferences for PrEP implants to inform optimal design.

Methods: We developed a discrete choice experiment and surveyed 800 young women in Harare, Zimbabwe and Tshwane, South Africa between September-November 2020. Women aged 18-30 years who were nulliparous, postpartum, or exchanged sex for money, goods or shelter in prior year were eligible; quotas were set for each subgroup. The DCE asked participants to choose between two hypothetical implants for HIV prevention in a series of nine questions. Implants were described by: size, number of rods and insertion sites, duration (6-months, 1-year, 2-years), flexibility, and biodegradability. Random-parameters logit models estimated preference weights.

Results: Median age was 24 years (interquartile range 21-27). By design, 36% had used contraceptive implants. Duration of protection was most important feature, with strong preference for a 2-year over 6-month implant. In Zimbabwe, the number of rods/insertion sites was second most important and half as important as duration. Nonetheless, to achieve an implant lasting 2-years, 74% were estimated to accept two rods, one in each arm. In South Africa, preference was for longer, flexible implants that required removal, although each of these attributes were one-third as important as duration. On average, biodegradability and size did not influence Zimbabwean women's choices. Contraceptive implant experience and parity did not influence relative importance of attributes.

Conclusions: While duration of protection was a prominent attribute shaping women's choices for PrEP implants, other characteristics related to discreetness were relevant. Optimizing for longest dosing while also ensuring minimal detection of implant placement seemed most attractive to potential users.

Keywords: Discrete choice experiment; HIV; Implant; Pre-exposure prophylaxis; Sub-Saharan Africa; Women.

Fig. 1

List of implant attributes with corresponding levels included in the discrete choice experiment. ¹Implant removal attribute assessed preference for whether the implant requires removal at the clinic by a health care provider versus dissolves on its own and does not need to be removed once all medicine has been released (made from biodegradable polymer). The attribute description stated that all implants can be removed by a health care provider after they are inserted, either for safety reasons or if the woman using the implant decides she no longer wants it

Fig. 2

Example choice set in discrete choice experiment survey. Participants were asked: “Which product would you use for HIV prevention?”

Fig. 3

Normalized average preference weights estimated using random parameter logit models, per enrollment location

Fig. 4

Preference share analysis for HIV prevention implant. Results from the random parameter logit models were used to predict the probability that the average participant in each geographic location would choose between two implants in three scenarios where Implant A has varying number of insertion sites and duration of protection and Implant B is 1 rod that lasts for 6 months (all other attributes held constant)