Big Events

Rapid review of the impacts of “Big Events” on people who use drugs and delivery of harm reduction and drug treatment services: Implications for strengthening systems in response to COVID-19.

Rapid review of research that focused on drug-related risks and harms, and/or service provision for people who use drugs in the context of major disruptive events. Data on “Big Events” including major hurricanes, economic recession, and heroin shortages were synthesized and visualized using risk pathway maps that highlight key outcomes and indicators. These results can serve to inform public health responses to the ongoing COVID-19 pandemic.


Big Events such as pandemics, natural disasters, and economic crises disproportionately impact marginalized peoples. People who use drugs are often socially and economically marginalized due to substance use disorders, comorbid mental disorders, low incomes, and social stigma.


This review aimed to better understand the varied effects of previous Big Events on risk behaviors and drug-related harms among people who use drugs, and on the delivery of harm reduction and drug treatment services. Equipped with this knowledge, public health officials and service providers will be better prepared to design and implement appropriate responses to the COVID-19 pandemic and to future public health crises.


  • Big Events generally lead to riskier drug use environments by disrupting drug markets, which in turn affects drug price, purity and availability. As people who use drugs respond and adapt to these changes, risk of harm may increase.
  • If a given Big Event causes harm reduction services to close, people may be more likely re-use and share needles and syringes, increasing their risk of blood borne viral infection. Several studies noted that increased risk behavior sometimes continued after a Big Event had resolved.
  • Big Events can cause changes in treatment demand and retention, although there were mixed findings on the direction of these effects.
  • Service providers may need to be prepared to provide harm reduction and treatment services for drugs that have not previously been widely used in their local area, and for different populations of people who use drugs.
  • Treatment outcomes were better for clients of services that were able to respond flexibly within their clinical guidelines and maintained lines of communication with clients during the crisis.
  • Adequate funding, space, staffing, transportation, training, and preparedness all play a role in maintaining service delivery during and after a Big Event. Service providers should be aware of potential psychological distress as a result of Big Events; in the COVID-19 context, this may include stress, anxiety, and grief.

Unfortunately, there is almost a complete lack of literature to inform responses to particular populations of people who use drugs, including women, Indigenous peoples, and visible minorities. This should be a research priority.


Canadian Institutes of Health Research, grant #442632

Principal Investigator

Co-investigators and collaborators

For further information

For more information, please contact Dr Sarah Larney at or consult the CIHR page.

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