Publication date: May 31, 2025
Background: The comparative risk of post-acute sequelae (PAS) associated with SARS-CoV-2 and influenza virus infection remains unclear. Methods: We undertook a retrospective cohort study within the Kaiser Permanente Southern California healthcare system of COVID-19 and influenza cases who received acute respiratory illness (ARI) diagnoses in virtual, outpatient, or inpatient settings between 1 September, 2022 and 31 December, 2023. We monitored PAS-associated healthcare utilization across all settings through 180 days after index ARI diagnoses. We estimated adjusted hazard ratios (aHRs) comparing COVID-19 cases to influenza cases, weighting to account for cases’ probability of retention in follow-up and infection with SARS-CoV-2 or influenza virus at the index ARI episode. Results: Analyses included 74,738 COVID-19 cases and 18,790 influenza cases, among whom 35,835 (38.3%), 26,579 (28.4%), 23,388 (25.0%), and 7,726 (8.3%) received care for their index ARI episodes in virtual, ambulatory, emergency department, and inpatient settings, respectively. Risk of PAS diagnoses in any clinical setting was similar among COVID-19 and influenza cases (aHR=1.04 [95% confidence interval: 0.99-1.09] and aHR=1.01 [0.97-1.06] 31-90 and 91-180 days after index, respectively). However, COVID-19 cases experienced higher risk of severe PAS conditions necessitating inpatient care (aHR=1.31 [1.07-1.59] and aHR=1.24 [1.03-1.49] 31-90 and 91-180 days after index, respectively). This heightened risk of severe PAS following COVID-19 was concentrated among patients who required inpatient admission at their index episode. Conclusions: PAS outcomes occur with similar frequency among non-severe COVID-19 cases and influenza cases. However, PAS among COVID-19 cases are more likely to require hospital admission than PAS among influenza cases.
| Concepts | Keywords |
|---|---|
| California | Acuity |
| June | Cases |
| Overweight | Cov |
| Rhinovirus | Covid |
| Vaccination2729 | Days |
| Diagnoses | |
| Higher | |
| Index | |
| Infection | |
| Influenza | |
| Inpatient | |
| Pas | |
| Risk | |
| Sars | |
| Setting |
Semantics
| Type | Source | Name |
|---|---|---|
| disease | MESH | sequelae |
| disease | MESH | influenza |
| disease | MESH | virus infection |
| drug | DRUGBANK | Aminosalicylic Acid |
| disease | MESH | COVID-19 |
| disease | MESH | infection |
| disease | MESH | emergency |
| disease | MESH | respiratory infections |
| disease | IDO | symptom |
| pathway | REACTOME | Influenza Infection |
| disease | MESH | death |
| disease | MESH | comorbidity |
| disease | IDO | history |
| disease | MESH | depression |
| drug | DRUGBANK | Ritonavir |
| drug | DRUGBANK | Oseltamivir |
| drug | DRUGBANK | Zanamivir |
| drug | DRUGBANK | Peramivir |
| disease | MESH | uncertainty |
| disease | MESH | Long COVID |
| disease | MESH | cognitive impairment |
| disease | MESH | Syndrome |
| drug | DRUGBANK | Carboxyamidotriazole |
| disease | MESH | Encephalitis |
| disease | MESH | Chronic fatigue syndrome |
| disease | MESH | swine influenza |
| disease | MESH | sepsis |
| drug | DRUGBANK | Guanosine |
| disease | MESH | breakthrough infections |
| disease | MESH | AIDS |
| disease | MESH | morbidity |
| disease | MESH | critically ill |
| disease | MESH | myocarditis |
| disease | MESH | asymptomatic disease |
| disease | MESH | Underweight |
| disease | MESH | Overweight |