1
Introduction
There have been substantial gains in the range and efficacy of technologies available
for HIV prevention, with voluntary medical male circumcision (VMMC), treatment as
prevention, and pre‐exposure prophylaxis (PrEP) being added to the existing toolbox
of condoms, lubricant, behaviour change, harm reduction, structural interventions
and advocacy programmes. These advances led to the optimism of calls to end the AIDS
epidemic by 2030 with a target of fewer than 500,000 new cases a year by 2020 and
200,000 by 2030 1, 2. However, progress towards these goals is slow with an estimated
1.9 million new infections in 2017 globally, including over a million in sub‐Saharan
Africa 3. Although these numbers represent a substantial reduction from the height
of the epidemic in the late 1990s, they are well off target despite intensive efforts
to promote HIV combination prevention encompassing structural, behavioural and biomedical
interventions. The targets were based on modelling which estimated the coverage needed
to achieve these reductions, namely meeting 90‐90‐90 treatment targets, 90% coverage
of key populations with combination prevention programmes, 90% reported condom use
rates with non‐regular partners and 90% male circumcision 2. However, investment in
prevention has been lower than required to achieve this coverage 4, and results from
trials of intensive population “test and treat” approaches show a lower impact than
hoped for, with up to 30% reduction in incidence, but with lower engagement and coverage
of younger people 5, 6.
Reducing incident infections is a key to sustainable HIV control, and epidemic models
suggest that further primary prevention is necessary in addition to treatment for
those already infected if the 2030 targets are to be reached 7. This all points to
the need for increased efforts in order to maximize the impact of technologies, including
those currently in development. While there is good evidence for efficacy of the technologies
and strategies in some populations 8, 9, they have failed to reach their potential
in many high incidence populations in sub‐Saharan Africa 10. In particular, the lack
of widely available efficacious female‐controlled methods has left many young women
vulnerable to HIV when their partners are unwilling to use condoms 11. While newer
technologies such as long‐acting injectable PrEP have potential for additional impact,
they too may disappoint if the lessons of existing programmes are not learned and
programmes not scaled sufficiently.
Adolescent girls and young women are at particular risk, accounting for 25% of new
HIV infections among adults in sub‐Saharan Africa, and with three to five times the
prevalence of adolescent boys and young men 7, 10. Reducing the high incidence in
these young populations is perhaps the most urgent global challenge, particularly
as 60% of the population in sub‐Saharan Africa is aged under 25 and absolute numbers
of young people will continue to rise over the coming decades 12.
It will be important to identify the mix of prevention technologies and approaches
that will meet the needs of these young people, in order to design the interventions
that will support their adoption. This requires an interdisciplinary approach, with
the appropriate mix of social, behavioural, epidemiological and programme science,
with learning from key stakeholders including young people themselves, service providers,
policy makers, industry and governments. The community perspectives about health and
HIV, and their health seeking behaviour need to be taken into account along with the
determinants of decisions about the HIV risk behaviours and the use of HIV prevention
technologies. Demographic, geographic and other characteristics should inform how
HIV prevention interventions are prioritized and should be designed around the needs
and preferences of priority users.
2
The technologies
Condoms provide triple protection against HIV, pregnancy and many other sexually transmitted
infections 13. They are often easily accessible, inexpensive and when carried provide
an option for unplanned sexual activity. Condoms have been promoted over the course
of the HIV pandemic with overall use increasing, reducing incidence among key populations
(men who have sex with men (MSM) and sex workers) where sexual partnerships can be
brief 14, 15. One important lesson from condom programmes in the general population
is that marketing and promotion are essential for generating demand. However, funding
for condom promotion and marketing has decreased, particularly since 2011, often leading
to condom supplies sitting unused due to lack of demand 16. The lack of demand may
reflect problems of access as distribution programmes have been cut and condoms may
be less widely available outside of health facilities in some countries. Perhaps the
most important lesson from male condoms is that an intervention for women that requires
partners to change their behaviour may be an insurmountable barrier to use in many
contexts, exacerbated by the perceptions that condoms decrease sexual pleasure and
may undermine trust in relationships.
Oral PrEP using tenofovir disoproxil fumarate and emtricitabine (TDF/FTC) is an efficacious
HIV prevention product. In developed countries oral PrEP use is reducing HIV incidence
among MSM 17. However, there are important barriers to its uptake and use: it is relatively
costly, so it can be difficult to access; it is specific for prevention and treatment
of HIV so its uptake and use can be stigmatized; it may have side effects when first
taken; it requires daily dosing to be effective for women; and it requires medical
monitoring for side effects and breakthrough infections 18. The introduction of oral
PrEP and its scale‐up has been slow for many reasons, but we are now in a position
where oral PrEP is being introduced for populations of MSM, sex workers, those in
HIV sero‐discordant couples, and young women in a small number of locations in sub‐Saharan
Africa. We are just starting to learn from oral PrEP programmes for young women and
there will be much to learn from their evaluation. Many future potential interventions
(such as cabotegravir injections, broadly neutralizing antibody [bNAb] injections,
ARV implants or vaccines) will not have daily use requirements, but will share many
of the same barriers to uptake as oral PrEP 19.
VMMC is another efficacious intervention and scale‐up across sub‐Saharan Africa has
been ongoing for several years with mixed effect, but over four million men were circumcised
in 2017 alone, and the programme has averted an estimated 230,000 HIV infections.
Comprehensive programmes including HIV testing and counselling, safer sex education
and condom promotion and distribution 20.
3
The HIV prevention cascade
HIV prevention programmes are complex to design, deliver and evaluate, and an HIV
prevention cascade has been suggested as a tool to support prevention programming
21. Such cascades identify key steps for interventions to be effective, including
identification of populations at risk, perception of risk, intervention uptake and
use, and ultimately the efficacy of the intervention. Once the cascade steps are identified
and quantified, programme planners can see where the largest gaps lie and take steps
to understand and address them. Figure 1 shows how prevention cascades may be used
at the programme level, starting from a population at risk and identifying who would
benefit from primary prevention packages, that is, those who test HIV negative or
who do not know their status. The options illustrated in the figure include VMMC for
young men, and condoms or oral PrEP for young men and women, and the cascades show
the potential gaps in protection.
Figure 1
Example of use of HIV Prevention Cascades at Programme Level. Diagram starts with
population at risk of HIV, identifies those who would benefit from a primary prevention
intervention package, and for each intervention identifies gaps in protection. For
one intervention, oral PrEP, the right side of the diagram suggests how a cascade
analysis can identify and address the largest gaps.
For example, defining who is at risk will depend on local HIV prevalence and patterns
of risk within the community. There has been relatively little recent work measuring
patterns of risk in young women, but in Southern and East Africa the risks include
transactional sex (broadly defined), age‐disparate partnerships, multiple sex partners,
alcohol use, being or having partners uncircumcised, partners who travel, and for
young women risk seems to increase with time after sexual debut and be associated
with marriage 22, 23, 24, 25. The first step of the cascade is perception of risk,
and studies of young women show that perceived risk of HIV acquisition is often lower
than actual risk. In various studies in sub‐Saharan Africa, between 17% and 50% of
women deemed to be at high risk of incident infection perceived themselves to be at
risk, while another study showed little association with self‐perception of HIV risk
and subsequent acquisition of infection 26. Understanding more about this mismatch
between risk and risk perception will be crucial to developing interventions to drive
demand and uptake for effective interventions. The next step would be for an individual
(and sometimes their partner) to take up and use an intervention. Many factors influence
such decisions, and the decisions have to be made and acted upon repeatedly in interventions
such as condoms, sexual behaviour change or PrEP use. Consistent use is a particular
challenge of HIV prevention: because there is low risk in most partnerships and high
risk in a small fraction, HIV prevention interventions have to provide protection
across all sex acts within those high‐risk partnerships for their benefits to be realized
27.
4
Social epidemiological framework
The prevention cascade can be used alongside a social epidemiological framework which
highlights the influence of structural factors, such as laws, policies, regulations,
relational factors, such as family, relationship status, economic situation and more
immediate factors, such as setting and privacy, intimate partner violence, alcohol
and drug use 28, 29. These factors will interact with people's preferences and motivations
to determine their use of any particular technology. Additional barriers to demand
for the uptake and use of interventions include lack of awareness, lack of self‐efficacy,
difficulty in accessing services, stigma associated with uptake (e.g. by health‐care
workers), stigma of use (e.g. by partners), difficulty of use and side effects of
use.
We can of course learn from examples where programmes have been effective. Reproductive
health programmes promoting access to contraception have been extremely successful
in many settings, despite requiring many similar behaviours and in similar contexts
to HIV prevention. Their successes have been put down to many factors, but key to
them are leadership and effective management, appropriate communication strategies,
evidence‐based programming, high quality contraceptive methods, availability, trained
staff, client‐centred care, choice of methods, access and variety of outlets, affordable,
involvement of men and women, and integration with other services 30, 31, 32. Effective
HIV prevention programmes for sex workers have also been based on community mobilization,
advocacy, access to integrated HIV prevention, STI control, contraception and other
services 14.
5
Banbury meeting and supplement
In 2017, a small meeting took place at the Banbury Center which hosts think‐tanks
on key questions in molecular biology, genetics neuroscience and science policy, on
how to maximize the impact of HIV prevention technologies in sub‐Saharan Africa 33;
we brought together international experts from different disciplines to address how
to make the development and delivery of HIV prevention technologies more successful.
The meeting concluded that many elements will be needed for effective and sustained
primary HIV prevention, including local ownership, community engagement and acceptability,
good evidence and data to guide planning and implementation and integration of primary
HIV prevention into local service prevision, including general sexual and reproductive
health services (Figure 2). The presentations and discussions at that meeting led
to the commissioning of this supplement with contributions addressing some of the
gaps in our knowledge, and showing the potential role of disciplines ranging from
mathematical modelling and social psychology to marketing and behavioural economics.
Figure 2
Model for maximizing HIV prevention impact at Programme level. Model developed through
consensus discussion at Banbury Center Meeting, May 2017 33. The outer boxes show
key characteristics and inputs of a theory‐ and evidence‐ based prevention programme
which are required to deliver the holistic intervention package.
In this supplement, we have brought together a number of articles that build on some
of the discussions at that meeting, representing a variety of disciplinary perspectives.
Mojola and Wamoyi start with a narrative and insightful review into the drivers of
HIV risk among young African women 34, and use insights from their own and others’
research to show how epidemiological, gender‐normative and environmental contexts
interact to drive hyperendemics of HIV, and how similar factors undermine preventive
interventions. Their deep descriptions of how social drivers result in risky settings
and behaviours are then used to suggest how that context can inform intervention planning.
In the next article, Skovdal draws on contemporary social theory to illustrate the
need for a greater understanding of the links between the different determinants of
preventive behaviours 35. He argues that through exploring social practices we can
better understand these phenomena, and proposes a “table of questioning” that can
be used by programme planners. The next paper is a viewpoint from Gomez and colleagues
who explore the application of market segmentation to prevention programmes 36. In
public health we are used to describing and grouping people by sociodemographic characteristics
that predict risk or define the need for an intervention. In marketing techniques
developed in the commercial sector, segmentation is based on a range of other factors,
psychographic and behavioural, which are said to better predict consumer behaviours.
The authors describe examples of market segmentation in public health, and argue that
we would do well to adopt some of these techniques to more closely match our programming
to the desires and preferences of the people we want to engage, developing segment‐specific
campaigns. This resonates with the broad interest in “personalized prevention,” but
it is clear that evidence is needed as to how and where such approaches are effective.
The next group of papers shift from frameworks to evidence from interventions. Celum
and colleagues provide a timely and comprehensive review of the state of knowledge
on pre‐exposure prophylaxis for adolescent girls and young women in Africa 37. The
paper summarizes lessons from PrEP implementation projects and concludes that these
are feasible interventions, but identified significant challenges; like Gomez they
identify the need for appropriate and targeted messages for demand creation; the need
for youth friendly and integrated services that address wider concerns such as sexually
transmitted infections and contraception; the need for novel approaches to supporting
adherence. Eakle and colleagues’ paper is a scoping review of the evidence on the
perspectives and experience of using PrEP among people at risk of HIV in sub‐Saharan
Africa 38. From 35 included papers, they were able to identify five themes which affected
acceptability and utilization. These resonate with many of the factors highlighted
elsewhere in this issue, including empowerment and stigma, complex risk environments
and relationships as well as specifics concerning efficacy, side‐effects and practical
challenges in use. This speaks to the need for more in‐depth research into user views
and priorities if current and future technologies are to be widely implemented. A
further review by Ensor and colleagues draws together quantitative and qualitative
evidence from 18 papers on the effectiveness of demand creation interventions for
male circumcision programmes 39. Financial incentives that compensate for loss of
income and costs have a large relative impact on uptake, but absolute effect was larger
in programmes involving community leaders and education.
Pettifor and colleagues conducted a qualitative study of a cash transfer project in
Tanzania, and propose a conceptual framework for the possible mechanisms for reducing
HIV risk 40. Reduced dependence on transactional sex may be one mechanism, but they
also identified the importance of business education and mentorship in building young
women's efficacy and self‐esteem, and argue that these may have a greater impact in
the long term. This kind of qualitative research is able to explore how interventions
work, an essential part of the transition from efficacy to implementation.
The final group of papers address the programme science of HIV prevention, which should
provide evidence of who to target with which interventions, how to evaluate, adjust
and continually strengthen programmes in response to feedback 41. Cowan and colleagues
use programme data to inform a mathematical model in order to assess whether scale
up of interventions for sex workers could contribute to elimination of HIV in Zimbabwe
42. They estimate that up to 70% of all new HIV infections could have been averted
if sex work interventions had achieved complete coverage in 2010; while they recognize
the limitations of this as a model, the paper raises an important point by showing
that appropriate scaling of interventions is essential if they are to have impact
at a population level. One obstacle to such scale‐up for programmes is cost, and this
is addressed in the paper by Roberts and colleagues 43. Using data from a PrEP implementation
project in Kenya, they identified costs of the programme and explored different scenarios
to show that incremental costs were sensitive to the delivery approach and the extent
to which monitoring, for example routine creatinine testing, were included. The paper
provides estimates that can be used to explore the cost‐effectiveness and budget impact
when providing PrEP that will be an import contribution to policy and practice with
this relatively new intervention. The paper has important implications for contemporary
discussions of different PrEP delivery models such as pharmacy‐based and direct to
consumer marketing.
In Kenya, HIV Prevention Cascades have been used as programme management tools, and
Bhattacharjee and colleagues describe their use in combination HIV prevention interventions
for sex workers 44. The paper shows that the cascade, while intended as a relatively
simple tool, can be quite complex in practice. The first challenge was to agree the
target population or denominator, which is challenging for relatively hidden and transient
populations, and then measures of uptake have to be defined. Despite these challenges,
they show how such data helped identify significant gaps in the programme, and by
using the same approach at a delivery level, service providers can reflect on and
improve their own performance. The final paper from Moorhouse et al. describes how
the HIV Prevention Cascade informed the identification and evaluation of interventions
in Zimbabwe 45. They propose a standard approach to the use of the cascade to develop
interventions.
6
Conclusions
Technological innovations hold enormous promise for improving health, and in HIV research
there have been remarkable advances in the development of efficacious tools for treatment
and prevention. Ensuring that these lead to maximum impact is just as much of a challenge
as developing the technologies themselves. In populations with the highest HIV incidence,
achieving impact will require the close collaboration of a wide range of stakeholders
and disciplines, political will, investment and ongoing evaluation and programme iteration.
The articles in this supplement have focused on some of the advances and insights
from diverse disciplinary backgrounds. The contributions have largely focused on young
women, which was an initial priority as we understand that they have often been failed
by previous programmes and technologies. Now that we have female‐controlled methods
the onus is on us to support women in accessing and using them. However, we recognize
this focus as a limitation, with men, particularly young men in Southern and East
Africa, also being at ongoing risk with limited access to the resources and methods
to protect themselves and their partners.
We hope that this journal issue will spark more interest in this evolving field and
contribute to the progress required to end AIDS.
Competing interests
All authors have no competing interest to declare.
Authors’ contributions
H.W. and G.G. drafted the manuscript, all authors contributed to revisions and approved
the final version.