Providing pre-exposure prophylaxis (PrEP) to people who need it entails at least nine
key steps, which can be conceived of as a PrEP continuum of care, according to
an article published online ahead of print by Amy Nunn and colleagues in AIDS. This continuum can help define
benchmarks by which progress in implementing PrEP in different programmes can
This is one of several recent articles which have attempted
to define a continuum of care for PrEP or other HIV prevention interventions,
adapting the concept of the ‘treatment cascade’ or the ‘continuum of care’ that
is used in relation to HIV treatment.
The HIV treatment continuum of care has helped identify the
sequence of events which are needed for treatment to have its desired effect –
diagnosis, linkage to care, retention in care, receiving HIV treatment and
adherence to it. Moreover, UNAIDS’ 90-90-90 targets reflect three key points
within this continuum of care. The targets have been used to focus attention on
improving uptake of key interventions that are essential to the health of
people living with HIV.
If there were consensus about the key steps in relation to
PrEP, this might also help focus attention and improve implementation.
Nunn and colleagues say that their model is based on
experience implementing PrEP in Providence, Rhode Island and other sites in the
United States. Each of the steps that are included presents opportunities for
patients to continue using PrEP or to disengage from care – they are therefore
important points of intervention.
The steps move from awareness to accessing healthcare, and then
to adherence and retention.
individuals at highest risk of HIV.
2. Increase those
individuals’ awareness of their risk of HIV.
3. Enhance those
individuals’ awareness of PrEP.
4. Facilitate access
to PrEP, in other words potential users schedule an appointment with a
suitable medical provider and have appropriate health insurance.
5. Link to PrEP care,
in other words potential users attend their appointment.
6. Prescribe PrEP
to those who meet clinical criteria.
7. Initiate PrEP:
users start to take the medications.
8. Adhere to PrEP:
users consistently take the medications.
9. Retain individuals
in PrEP care.
The authors note that defining who is retained in care is
challenging. PrEP is understood to be appropriate for ‘seasons of risk’, so
many people will withdraw from PrEP care in a way that is entirely appropriate.
Retention should be measured with reference in four distinct groups of people –
individuals who need PrEP who are retained in care, individuals who need PrEP
who are not retained in care, individuals who no longer need PrEP, and
individuals lost to follow-up.
In this publication, the authors don’t propose data sources
that could be used to compare different programmes or localities. Just as many countries
have difficulty estimating the proportion of people living with HIV who remain
undiagnosed (for measuring progress to 90-90-90), having reliable data to estimate
the size of the population at highest risk of HIV and the proportion of that
group aware of PrEP will be challenging in many settings. Nonetheless, setting
targets may spur data collection.
The model builds upon and adds additional stages to a continuum
that was published by Colleen Kelley and colleagues in 2015. That was a
four-stage continuum (aware of PrEP and willing to use it; have access to
healthcare; eligible for PrEP; adhere to PrEP). The new model suggests that the
continuum of care is more complex and suggests a series of opportunities for
However a simpler continuum might be more useful for setting
targets and as an advocacy tool. For example, by including access to healthcare
as one of the four stages in the continuum, Kelley focuses attention on the way
in which exclusion from health insurance restricts the uptake of PrEP in the
And while these models may appear comprehensive, it is
notable that they do not fully encompass one of the three key stages of the HIV
prevention cascade that were described by James Hargreaves and colleagues in The Lancet HIV last year. According to Hargreaves, for any HIV
prevention product, procedure or behaviour we need to consider supply, demand and adherence. By including awareness, adherence and retention, Nunn’s
continuum reflects the latter two.
But it focuses attention on the individual who may take PrEP
and can only indirectly measure problems with the supply of PrEP, in other
words problems with the health system. The coverage of PrEP could be low
because only a few clinical services offer PrEP, they are inappropriate for the
people who need it, or physicians have doubts about the merits of PrEP.
interventions needed to increase the coverage of PrEP might not only be demand-creation
or adherence-support, but the creation of more accessible health services, services to help people obtain health insurance, physician education, or the removal of legal barriers to providing PrEP to people under the age of 18.