Estimates of people who injected drugs within the last 12 months in Belgium based on a capture-recapture and multiplier method

Background

For Belgium, available estimates of the number of people who inject drugs (PWID) are based on data from more than fifteen years ago and apply only to those who report ever injecting drugs. As a result, no reliable baseline data exist to determine the scale of services for PWID.

Methods

We obtained pseudo-anonymized identifier information from treatment and harm reduction service providers and a fieldwork study between February and April 2019 in Brussels. We estimated the number of PWID, defined as people who injected within the last 12 months, in Brussels using capture-recapture (CRC) methodology. To obtain national estimates, we scaled the proportion of PWID in Brussels to the total number of this population in Belgium based on two existing drug treatment registers, which were then multiplied with the result of the CRC.

Results

The total population of PWID is estimated to be 703 (95%CI 538 – 935) for Brussels and between 6,620 (95%CI 4,711 – 8,576) and 7,018 (95%CI 4,794 – 9,527) for Belgium.

Conclusions

These estimates provide crucial information to ensure that services to PWID are adequately maintained. They clearly indicate the need to maximize efforts to achieve the targets set by WHO for 2030 on the provision of 300 sterile needles and syringes per PWID per year, a 90% reduction of new HCV infections, and a 65% reduction of liver-related mortality.