Impact of changes to the delivery of opioid agonist treatment, introduced during the COVID-19 pandemic, on treatment access and dropout in Ireland: An interrupted time series analysis

Background: Following the emergence of COVID-19, Ireland introduced national contingency guidelines to ensure rapid and uninterrupted access to opioid agonist treatment (OAT). This study aims to assess the impact of changes introduced to the delivery of OAT on the number of people accessing treatment and treatment dropout.Methods: The study conducted interrupted time series analyses, with separate segmented regression models (March 2019-February 2020) vs (April 2020-March 2021), for (A) total number of people accessing OAT, (B) the number initiating treatment, and (C) the number dropping out of treatment, using data from the National OAT treatment register. The study examined immediate (change in level or intercept: beta(2)) and long-term impacts (change in slope; i.e., the difference between the slope before and after the intervention: beta(3)). We performed total and stratified analyses by gender, age group (<40/>= 40 years), and OAT drug (methadone or buprenorphine).Results: A total of 10,251 people accessed OAT in Ireland in March 2019 (2 % buprenorphine, n = 178), increasing to 11,441 (4 % buprenorphine, n = 471) in March 2021. The study observed an immediate (beta(2) = 504.3, p < 0.001) and continued (beta(3) = 31.9, p < 0.001) increase of people accessing treatment following the introduction of the OAT contingency guidelines. In contrast, observed changes in level and slope were not significant for treatment initiation or dropout. The study did find, however, a modest reduction in dropout among those receiving buprenorphine (beta(3) =-0.6, p = 0.036).Conclusions: Changes introduced to the delivery of OAT, under the COVID-19 contingency guidelines, are associated with increased access to OAT in Ireland, with no evidence of increase in treatment dropout. Whether these effects will be maintained over time remains to be seen.