Acute and post-acute healthcare utilisation after Delta and Omicron BA.1/2, BA.4/5, XBB infection: a cohort study

BackgroundElevated risk of healthcare utilisation in the post-acute phase following SARS-CoV-2 infection is well-documented. However, the burden of acute and post-acute healthcare utilisation following milder Omicron infection is unknown. MethodsWe utilized the Singaporean national SARS-CoV-2 testing registry to construct cohorts first infected with SARS-CoV-2 during periods with community transmission predominated by Delta, Omicron BA.1/2, Omicron BA.4/5 or Omicron XBB contrasted versus contemporaneous test-negative controls. We estimate the excess risks/rates/burdens of all-cause (1) hospitalisation (2) ICU admission (3) emergency-department (ED) utilisation and (4) total healthcare costs incurred by SARS-CoV-2-infected individuals in acute (0-30 days) and post-acute phases (31-300 days) following infection. Outcomes were compared across variants, vaccination doses and severity of infection. Results1,678,678 test-positives were contrasted against 3,346,910 test negatives from 2021-2023. Risks of all-cause hospitalisation, ED visits and overall healthcare costs incurred were significantly higher amongst SARS-CoV-2-infected individuals compared with test-negatives, in both acute and post-acute phase; while risk of ICU admission was elevated only in the acute phase for SARS-CoV-2-infected individuals. In the acute phase, excess risks of healthcare utilisation were elevated 3.6-21.9 times. In the post-acute phase, excess risks of any healthcare utilisation were elevated 0.18-2.02 times, in SARS-CoV-2-infected individuals. Fully vaccinated (2 doses) or boosted (3+ doses) decreased risks and rates of any ED visits, inpatient/ICU admissions and incurred lower excess healthcare costs in both the acute and post-acute period, versus individuals with 0/1 doses. ConclusionsHealthcare utilisation was elevated up to 300 days post-SARS-CoV-2 infection, when compared against test-negatives; even when milder Omicron infection predominated community transmission.