This section introduces the evidence for the effectiveness of
interventions that encourage people to adopt behaviours that reduce their risk
of HIV infection. It also looks at evidence for interventions designed to help
HIV-positive people to minimise their risk of transmitting HIV.
There is a demand amongst funders and practitioners for
evidence that particular HIV-prevention methods work. The phrase
‘evidence-based prevention' has been coined to describe the need for HIV-prevention
activities to be developed in line with evidence regarding risk factors and
In general, calls for an evidence-based approach follows
calls in NHS clinical practice for better outcomes through the adoption of ‘evidence-based
medicine’, i.e. interventions whose efficacy has been demonstrated in sound
In particular, there is evidence that condom use is at best
static and at worst declining amongst some at-risk populations, notably gay men
in richer countries.1,2 This
has led to demands both for better and more assertive behavioural
interventions, on the one hand, and increased emphasis on treatment as
prevention and biomedical prevention, on the other. This is a much-politicised
area and, therefore, one in which gathering evidence on the effectiveness of
interventions may help shed light in heated debates.
The call for evidence-based prevention is only part of a
wider demand that health-promotion activities, psychotherapy and counselling,
and other non-drug-based interventions are subjected to the same kind of
scrutiny as drug treatments. The potential for harming patients with untested drug
treatments is obvious. The same applies to biomedical-prevention methods. For
example, the spermicide nonoxynol-9 killed HIV in the test tube, but was found
to facilitate transmission in real life.3
Behavioural-prevention programmes that are not evidence based
and well thought out are less likely to do harm and may simply waste money. However,
there are occasional examples of ones that produce significantly worse health
outcomes than doing nothing. In a recent meta-analysis of adherence
interventions, for instance,4 most interventions were positive or neutral in their effect. There was, though,
one trial in which 40 participants wrote about an optimistic future in which
they would only take one medication a day; this had a significantly negative
effect, with nearly 60% worse adherence in the intervention group.
One large meta-analysis5 of
in HIV prevention, which we examine in more detail below, found that programmes
that used threat-inducing arguments to encourage condom use (such as the fear
of pregnancy) and normative arguments (‘everyone else does it, you should too’)
had significant negative effects across participants as a whole, though there
It is, therefore, important to review the effectiveness of
prevention programmes, as to do otherwise would not only waste public money,
but might increase HIV infections.
This section reviews:
- How and why we measure whether HIV-prevention
efforts have worked, and issues in measuring effectiveness.
- The evidence provided by some large systematic
reviews and meta-analyses of HIV-prevention programmes.
- The underlying philosophies of HIV prevention:
how and why people change their behaviour.