Clinical severity of Omicron and Delta SARS-CoV-2 infections in children

We aimed to compare the clinical features and severity of the Omicron and Delta variant infections among children hospitalized for coronavirus disease 2019 (COVID-19).

Children 12 years old or less hospitalized for COVID-19 across five hospitals between January 1, 2021 and March 31, 2022 were identified using the state's pediatric COVID-19 registry. Delta and Omicron-infected patients without previous COVID-19 infection, COVID-19 vaccination, or co-infections were propensity-score matched 1:1 to control for differences in baseline characteristics. Clinical manifestations, treatments, and outcomes were analyzed. Disease severity was assessed using an adapted WHO ordinal scale.

Of the initial 1367 patients, 668 had Delta infection and 699 had Omicron infection. Propensity-score matching produced 558 matched pairs. Patients with Omicron infection were more likely to present with croup (the odds ratio, OR, was 10.87, with a 95% confidence interval, CI, ranging from 2.54 to 46.59), lower respiratory tract infection (OR 2.32, 95% CI, 1.48-3.64) and seizures (OR 8.39, 95% CI, 5.04-13.99) compared with those with Delta infection. Omicron was associated with increased odds of moderate/severe disease (OR 6.14, 95% CI, 4.72-7.99) and a greater need for intravenous fluid therapy (OR 6.00, 95% CI, 4.29-8.39), corticosteroids (OR 3.08, 95% CI, 1.66-5.72), empirical antibiotics (OR 1.70, 95% CI, 1.10-2.64), and low-flow nasal oxygen therapy (OR 3.68, 95% CI, 2.17-6.22) in comparison with Delta.

Children hospitalized with Omicron infection demonstrated a distinct clinical profile compared to those with Delta infection, with increased likelihood of moderate/severe disease and higher utilization of health-care resources.