9 The evidence

What evidence is the guidance based on?

Updated guidance

The evidence that the Public Health Advisory Committee (PHAC) considered included:

In some cases, the evidence was insufficient and the PHAC has made recommendations for future research. For the research recommendations and gaps in research, see recommendations for research and gaps in the evidence.


The evidence statements from 2 reviews conducted for the original guidance and 2 reviews conducted for the updated guidance are provided by external contractors. In addition, they provided consensus statements from the policy review and consensus development exercise.

This section lists how the evidence statements and the consensus statements link to the recommendations and sets out a brief summary of findings from the economic analysis and the fieldwork.

This section also sets out a brief summary of findings from the economic analysis conducted for the original guidance.

Economic modelling

The analyses for the original guidance estimated that needle and syringe programmes used as a channel for treating injecting drug users for chronic hepatitis C were cost effective. They can reduce the costs for society of drugs misuse by:

  • improving the health of people who inject drugs

  • ensuring the disease cannot be passed on after treatment.

The modelling showed that if only health costs and benefits are counted, then a needle and syringe programme that increased coverage by 25% in a city with a high incidence of hepatitis C virus was cost effective (estimated ICER £11,400). However, an increase in coverage by 12.5% was not cost effective (estimated ICER £31,600). For a low-incidence city, the estimated ICER for an increase in coverage of 25% was £11,800, whereas for an increase of 12.5% the ICER was estimated as £26,100.

If the costs to the criminal justice system are included, the modelling showed that a 12.5% increase in coverage for a high-incidence city was not cost effective (estimated ICER £38,700). But if coverage increased to 25%, the estimated ICER fell to £19,900. For a low-incidence city, for a 12.5% increase in coverage the ICER was £29,300, and for a 25% increase in coverage the ICER was £12,300.

Needle and syringe programmes can also help reduce the number of people who are injecting drug users by acting as a 'gateway' to opiate substitution therapy. So these programmes may help reduce the costs of drug-related crime. When these indirect ('gateway') effects were modelled, it showed that a 13.5% increase in the rate of referral to opiate substitution therapy resulted in ICERs of between dominant and £17,000, depending on prevalence.

The modelling found that overall, it is cost effective to give users more than one free needle per successful injection, if the cost of reaching them is not excessive and if use of this service increases by more than about 25% as a result.

Full details can be found in Assessing the cost-effectiveness of interventions linked to needle and syringe programmes for injecting drug users: an economic modelling report.

There were no additional analyses undertaken for the updated guidance.

Fieldwork findings

The fieldwork aimed to test the relevance, usefulness and feasibility of putting the recommendations into practice. The PHAC considered the findings when developing the final recommendations..

Fieldwork participants who work with people who inject drugs were very positive about the recommendations and their potential to improve needle and syringe programmes. Many participants stated that the new recommendations about young people and about people who inject image- and performance-enhancing drugs were much needed and would be very useful.

  • National Institute for Health and Care Excellence (NICE)