Features of COVID-19 in Children During the Omicron Wave Compared With Previous Waves in Madrid, Spain

Abstract

To the Editors: The SARS-CoV-2 variant Omicron (B.1.1.529) replaced other variants in Spain during the sixth wave, accounting for 79%–94% of positive samples in the last 2 weeks of 2021.1 The information is scarce about Omicron severity in children. To describe the features of children with COVID-19 during the Omicron wave, we reviewed charts from children with COVID-19 attended at the emergency room of a secondary center in Spain from December 20, 2021, to January 2, 2022. All patients’ charts were reviewed 1 week after diagnosis to check complications. The detection by reverse transcriptase-polymerase chain reaction (RT-PCR) used as target genes ORF1ab and N of the SARS-CoV-2 genome. All samples with a cycle threshold (Ct) <25 were analyzed with a second RT-PCR with probes targeting the gen S mutations consistent with Omicron. This study is part of the study EPICO-AEP.2 A total of 1,360 children were attended at the emergency room during the study period. Globally, 94 (6.9%) had a positive RT-PCR for SARS-CoV-2, with a median age of 6.5 years (interquartile range: 1.3–9.7), and 82.9% had fever. Of them, 15 (16.0%) had a Ct <25: 13/15 (86.7%) were identified as Omicron and 2/15 (13.3%) as Delta variant. Only 2 of 94 (2.1%) patients were hospitalized: a 3-year-old girl with features of bacterial pneumonia and confirmed Omicron variant, and a 40-day-old infant with whooping cough. No patient needed pediatric intensive care unit admission or died. In a study performed by our group during the third wave, caused predominantly by the Alpha variant, 3/75 (4.0%) children with COVID-19 were hospitalized, not differently to the Omicron wave (P = 0.394), and one child needed pediatric intensive care unit admission. To better describe the profile of children with Omicron, we identified 17 further children with Omicron attended at another center. We compared the features of the 109 ambulatory children attended during the Omicron wave in these 2 centers to 546 ambulatory children attended in previous waves in 35 centers, from March 2020 to October 2021, included in the national COVID-19 EPICO-AEP registry (Table 1).2 During the Omicron wave, more children presented upper respiratory tract infection, but fewer children had pneumonia. Fever, headache, and diarrhea were more common during the Omicron wave. TABLE 1. - Comparison Between Features of Ambulatory Children Attended During the Omicron Wave and Previous Waves at the Emergency Rooms Features Previous Waves N = 546 (%) Omicron Wave N = 109 (%) P Sex (female) 289 (52.9%) 60 (55.0%) 0.686 Age (yrs), median (IQR) 5.7 (1.1–11.7) 6.6 (1.3–9.8) 0.330 Age band (yrs) <0.001 0–4 259 (47.4%) 47 (43.1%) 5–12 162 (29.7%) 54 (49.5%) 12 or above 125 (22.9%) 8 (7.3%) Comorbidity 99 (18.1%) 12 (11.0%) 0.070 Contact with household confirmed case 240 (44.0%) 33 (30.3%) 0.008 Symptoms/signs Fever 371 (67.9%) 90 (82.6%) 0.002 Cough 264 (48.4%) 61 (56.0%) 0.147 Sore throat 99 (18.1%) 20 (18.3%) 0.957 Runny nose 197 (36.1%) 49 (45.0%) 0.081 Fatigue, malaise 73 (12.2%) 12 (11.0%) 0.728 Wheezing 23 (4.2%) 2 (1.8%) 0.237 Headache 88 (16.1%) 35 (32.1%) <0.001 Myalgia 48 (8.8%) 4 (3.7%) 0.071 Diarrhea 75 (13.7%) 23 (21.1%) 0.049 Vomiting 91 (16.7%) 23 (21.1%) 0.265 Syndromic diagnosis* Upper respiratory tract infection 195 (37.0%) 73 (67.0%) <0.001 Flu-like 80 (15.2%) 14 (12.8%) 0.532 Fever without a source 84 (15.9%) 5 (4.6%) 0.002 Gastroenteritis 40 (7.6%) 7 (6.4%) 0.671 Pneumonia 38 (7.2%) 1 (0.9%) 0.013 Asymptomatic 44 (8.3%) 3 (2.8%) 0.042 Bronchitis/asthma flare 18 (3.4%) 2 (1.8%) 0.389 Bronchiolitis 2 (0.4%) 0 (0.0%) 0.519 Categorical variables are compared using the χ2 or Fisher tests, and continuous variables using Wilcoxon rank-sum test. Significant P values (<0.05) are in bold.*The syndromic diagnosis was not recorded in 19 cases diagnosed in previous waves; percentages and P values are calculated omitting those cases. Notably, most patients during the Omicron wave were ≤11 years old. Nearly 83% of adolescents ≥12 years old are vaccinated in Spain, which may explain the low proportion of adolescents in our population. Some studies reported that around 1%–2% of children with COVID-19 need hospitalization, likewise our study.3,4 This study suggests that children with the Omicron variant do not have a worse outcome than children with previous variants. Omicron in children seemed to have a similar clinical profile but with increased tropism for the upper airway and less tropism for the lungs. ACKNOWLEDGMENTS We thank all the patients and families for their participation in this cohort, the staff members who cared for them at their personal risk in this time of epidemics and pediatricians who cared for the patients and helped gathering data including: Teresa Reinoso, Alfonso Cañete and Ane Plazaola (Hospital Universitario Infanta Sofía), David Melero, Angela Somodevilla and Raquel Guillén (UR Salud).

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