Study population and setting
This retrospective cohort study included 315 individuals diagnosed with laboratory-confirmed SARS-CoV-2 infection from March 25 to May 15, 2020, and 1,402 individuals diagnosed with influenza A or B from October 1, 2019 to June 6, 2020 at Children’s National Hospital in Washington, DC. COVID-19 patients were identified from an infectious disease database, and influenza patients were identified from the laboratory informatics system. Testing for COVID-19 and influenza were performed on US FDA-approved PCR assays. Asymptomatic COVID-19 patients who tested positive during pre-admission of pre-procedural screening were excluded.
Summary of Main Findings
Of the 315 COVID-19 patients (52% male, median age: 8.4 years [range: 0.03-35.6 years]), 54 (17%) were hospitalized, 18 (6%) were admitted to the ICU, and 10 (3%) received mechanical ventilation (average duration 10.1 days). These proportions were similar to those seen among the 1,402 influenza patients (53% male, median age: 3.9 years [range: 0.03-40.4 years]): 291 (21%) were hospitalized, 98 (7%) were admitted to the ICU, and 27 (2%) received mechanical ventilation (average duration 7 days). None of these differences in outcomes were statistically significant. Hospitalized COVID-19 patients were older (n=54, median age 9.7 years, 37% ≥15 years) than hospitalized influenza patients (n=291, median age 4.2 years, 6% ≥15 years). None of the patients with COVID-19 died, and only 2 patients with influenza (0.1%), both with influenza A, died. Patients hospitalized with COVID-19 (vs. influenza) were also more likely to have an underlying medical condition (65% vs. 42%), and more often presented with a fever (76% vs. 55%), cough (48% vs. 31%), diarrhea or vomiting (26% vs. 12%), body aches (22% vs. 7%), chest pain (11% vs. 3%), or headaches (11% vs. 3%). The age distribution and symptoms of influenza A and B patients were similar.
The study compared COVID-19 and influenza patients drawn from the same general population over similar time periods.
This was a single-site study, and results may not be generalizable to other settings. Although most patients were children, it is unclear why the study included a small number of adults; results were not disaggregated by age group. None of the statistics presented were adjusted for confounders, and confounding is likely. Due to limited sample size, comparisons between COVID-19 patients and influenza patients who were admitted to the ICU or who received mechanical ventilation were not presented. Testing for influenza was available throughout the study period, but the test positive rate decreased dramatically following school closures on March 15, 2020 (there was only one case after March 22), and it is possible that there are unmeasured differences in the populations who received testing for influenza before and during the COVID-19 pandemic. Comparisons of patients hospitalized for influenza and flu may be influenced by ascertainment bias if testing practices or symptom screening differ based on an individual’s diagnosis. Similarly, the thresholds for a hospital visit may have differed before and during the pandemic, which could bias comparisons of hospitalization rates and outcomes between influenza and COVID-19.
This is one of the first studies to compare clinical features between COVID-19 and seasonal influenza in children.