Reduced economic disparity in biologics use for psoriasis after introducing the reducing copayment program.

Biologics for psoriasis are efficient and safe, but very expensive. We investigated the association of the reducing copayment program (RCP) with changes in biologics use patterns depending on the income levels of patients with moderate-to-severe psoriasis. This nationwide cohort study included patients identified as having moderate-to-severe psoriasis between 2014 and 2020. Logistic regression models were used to estimate the odds ratio for the use of biologics according to income levels. Among 57,139 patients with moderate-to-severe psoriasis, 3464 (6.1%) used biologics for psoriasis from 2014 to 2020. After the introduction of RCP in 2017, the proportion of patients with moderate-to-severe psoriasis using biologics rapidly increased from 5.0% in 2016 to 19.2% in 2020; the increase was more remarkable in patients with the lowest or mid-low income compared to those with Medical Aid. Drug survival of biologics was higher in patients with the highest income before the RCP, but became comparable between those with high and low incomes after RCP introduction. The introduction of RCP was associated with an increased use of biologics in patients with moderate-to-severe psoriasis of all income levels; however, the effect was more pronounced in low-income patients. The RCP may contribute to alleviating the disparity in access to biologics.