COVID-19 and subsequent new allergy drug prescriptions: a matched cohort study in Japan

Emerging evidence indicates that COVID-19 may increase the incidence of new allergic conditions requiring medication. This matched cohort study investigated the impact of COVID-19 on new allergy medication prescriptions utilizing Japan’s National Insurance Claims Database. The study compared the incidence rate ratio (IRR) and difference (IRD) of new prescriptions for H1 antihistamines, leukotriene receptor antagonists, eye drops, and nasal sprays between groups. Additionally, subgroup and sensitivity analyses were conducted to evaluate the heterogeneity among subgroups and the long-term effects of COVID-19 on allergy medication prescriptions. A total of 778,362 Patients with COVID-19 and matched controls were followed for a median of 7 months. The IRR for new prescriptions of H1 antihistamines, leukotriene receptor antagonists, eye drops, and nasal sprays was 1.21 (95% CI, 1.2–1.23), with an IRD of 1,528 per 1,000,000 person-months (95% CI, 1,492–1,564). Subgroup analyses showed higher IRRs for individuals aged ≥ 65 years (IRR: 1.33, 95% CI: 1.31–1.35) and those with Charlson Comorbidity Index (CCI) scores ≥ 4 (IRR: 1.35, 95% CI: 1.31–1.38). Sensitivity analyses IRRs remained higher than controls, particularly in older adults and those with higher CCI scores. Age ≥ 65 years (IRR: 1.14, 95% CI: 1.11–1.18) and CCI scores ≥ 4 (IRR: 1.17, 95% CI: 1.11–1.23) were significant even after 1 year. These findings suggest COVID-19 may have a lasting impact on the incidence of new allergy medication prescriptions, especially in vulnerable populations, underscoring the need for continued monitoring and personalized post-COVID-19 support.