Syringe Dead Space and hepatitis C infectivity

The Total Dose needles and other dead space reduction measures have had their effectiveness at reducing hepatitis C infectivity tested by Professor Robert Heimer's team at Yale University, and the results published in the online journal PLOS ONE in November 2015.

To read the evaluation in full, click: here.

This article was last updated 8/1/2016.

The central messages of this paper are that:

• Insulin type fixed needle syringes have the lowest blood borne virus transmission risk;
  

• Rinsing syringes before reuse with water and bleach is an effective and essential process for the prevention of both HIV and hepatitis C, and should be encouraged (the evidence for this with hep C is here and for HIV here);
  

• For people who are unable, or cannot be persuaded, to use insulin type syringes, and instead use 2ml or 5ml syringes for detachable needles, the Total Dose needles are, overall, the best of the dead space reducing measures available - and reduce the dead space more than syringes with modified plungers.
  

• The more the dead space is reduced, the greater the effect on HCV infectivity, and that this is most marked when the syringes had been stored for a few days.
  

This was a reassuring finding. There was previously the concern that as catching an infection is a binary thing – either the virus is transmitted
or it isn’t – that the reductions in dead space might not be enough to prevent infections. Now it is clear that incremental reductions in the dead space lead to a reduction of infection risk.

Using Total Dose needles compared to standard needles gave gains of up to 65% reduction in HCV; and 6 fold in HCV reduction after 3 days. Total Dose needles give better protection from hepatitis C than syringes with displacement spikes.

Rinsing and storage
Because people often rinse syringes after use, and again before reuse (especially if the reuse isn't on the same day) real life rinsing practice of injecting drug users often exceeds the 1 or 2 times in the study. In these cases the HCV reductions will be greater than the 1 - 2 rinses performed in the study.

We know from Avril Taylor’s research (that led to the development of the colour coded Nevershare syringes) that equipment is often stored and reused some time later, so in these cases because of reduced viral survival when there is less blood, reducing the dead space could make the difference between someone catching hepatitis C and not.

An important intermediate step
There is no suggestion that we have achieved risk equivalence with insulin-type syringes, or that Total Dose needles are the end point in reducing dead space in syringes for detachable needles. Indeed, while the research was in progress, the tool that makes the 25g Total Dose hub was being replaced with a new one that makes the hubs with an extension on the spike to reduce the dead space by a further 27 micro litres, which would make the performance closer to that of the 23g needles used in the experiment.

The Total Dose dead space reducing needles therefore represent an important step forwards, and are an intermediate step between high dead space injecting equipment, and insulin type low dead space syringes for those people who need to use higher volume syringes, or longer/thicker needles than are available on insulin syringes (an example here) for the prevention of hepatitis – and there is room for optimism that the impact on HIV prevention will be greater.

We are, of course, working to further reduce the dead space in detachable needle and syringe combinations, and demand for the Total Dose needles is helping us maintain momentum with this process.

Recommended practice
Low Dead Space equipment is recommended by the World Health Organisation Guidance on prevention of viral hepatitis B and C among people who inject drugs, which has the recommendation that:

• "...needle and syringe programs also provide low dead-space syringes for distribution to people who inject drugs."
  

It is also recommended in the Consolidated Guidelines HIV prevention, diagnosis, treatment and care for key populations:

• 'All individuals from key populations who inject drugs should have access to sterile injecting equipment through needle and syringe programmes...
  

• It is suggested that needle and syringe programmes also provide low dead-space syringes (LDSS) along with information about their preventive advantage over conventional syringes...
  

• Injecting equipment should be appropriate to the local context, taking into account such factors as the type and preparation of drugs that are commonly injected (p. 31).