Trends in self-reported non-fatal overdose and patterns of substance use before and during the COVID-19 pandemic in a prospective cohort of adults who have injected drugs - Baltimore, Maryland, 2014-2022

Background: Overdose deaths increased during the COVID-19 pandemic in the United States. Less is known about drug use behavior changes during the same time period. We examined differences in non-fatal overdose and drug use behaviors before and after the start of the COVID-19 pandemic in a community-recruited cohort of adults who have injected drugs.Methods: 721 participants attended 7401 visits between Jan 2014 and Mar 2022. Outcomes (non-fatal overdose, drug route of administration, type of drugs used) were assessed via self-report in the last six months. We compared pre-pandemic (Jan 2014-Mar 2020) to inter-pandemic (Dec 2020-Mar 2022) prevalence of each outcome using Cohcrane-Maentel-Haeszel odds ratios (CMH-OR). We then estimated probabilities for transitioning between specific behaviors from participants' last pre-pandemic visit to their first inter-pandemic visit.Results: Comparing pre-pandemic visits to inter-pandemic visits, the prevalence of non-fatal overdose did not change (CMH-OR 1.06, 95% CI 0.75-1.50); the prevalence of injection (CMH-OR 0.13, 95% CI 0.1-0.17) and non-injection (CMH-OR 0.51, 95% CI 0.42-0.61) drug use declined. More than a third (35.7%) of persons using both injection and non-injection drugs pre-pandemic transitioned to exclusive non-injection use during the pandemic. By contrast, few (4.0%) persons using non-injection drugs exclusively pre-pandemic transitioned to injecting during the pandemic.Conclusion: Among adults who have injected drugs, the start of the COVID-19 pandemic was associated with a reduced drug use prevalence and transitions from injection to non-injection use. Average overdose prevalence was unchanged, but these behavior changes may have helped mitigate overdose harm.