Did Hospitalization Age Decrease in Children in the Omicron (B.1.1.529) Era?

İngilizce (OpenAlex)

To the Editors: In mid-January 2022, it was announced by the Turkish Ministry of Health that the dominant variant in circulation is Omicron. A recent study from our center revealed that every variant reported before had different features, and the one before the Omicron variant, Delta variant (B.1.617.2), was associated with higher hospitalization rates.1 We also compared the changing hospitalization trends of pediatric patients before and during the Omicron period in terms of age groups. Between March 2020 and January 2022, a total of 660 pediatric COVID-19 patients were reviewed retrospectively. The patients were classified into 4 age groups as <12 months, 12–71 months, 72–143 months, and ≥144 months. Of all patients, 576 were hospitalized before the Omicron era, and 84 were hospitalized during the Omicron era. The median age of the children hospitalized before the emergence of the Omicron variant was 71.5 months (min. 1 month to max. 17 years 10 months), and 23.3% of the patients were under 12 months. In the second group, the median age was 15 months (min. 1 month to max. 17 years), and 41.7% of the patients were under 12 months. The rates of the hospitalized patients 12 years and above before and during the Omicron era were 34% and 13.1%, respectively (Table 1). The average age of the patients hospitalized during the Omicron era is significantly lower compared with the previous period (P < 0.001). The share of patients under 12 months among all hospitalized patients has nearly doubled in the Omicron era; and it was found that the rate of patients 12 years of age and older has decreased to almost one-third. TABLE 1. - Rate of Hospitalized Patients Before and After the Emergence of the Omicron Variant Before Omicron (Other Variants) (%) During Omicron Period (%) P <12 mo 23.3 41.7 0.0018 12–71 mo 26.7 35.7 >0.05 72–143 mo 16 9.5 >0.005 ≥144 mo 34 13.1 0.0014 Although reports from South Africa and England indicate that hospitalization rates are lower following Omicron infection compared with the Delta variant infection,2,3 according to Scientific Advisory Group for Emergencies in the United Kingdom, hospital admissions of children under 1-year-old have risen significantly.4 Centers for Disease Control and Prevention (CDC) reported that the rate of COVID-19-linked hospitalizations among children younger than 5 grew substantially between December 26, 2021, and January 1, 2022, whereas the same rate for children between the ages of 5 and 17 remained relatively stable.5 However, it is controversial if it is due to the vulnerability of this age group to the Omicron variant. A possible reason for the increase in hospitalizations in this group may be that the overall number of cases has increased due to high transmissibility and the relative difficulty of eliminating the risk of serious bacterial infections in younger children. Immunization of children 12 years and above in Turkey started in September 2021. However, considering insufficient data on vaccination rates in this age group in Turkey, it is difficult to determine if the decrease in hospitalization in the age group 12 years and above is due to vaccination. Although the vaccination program in Turkey does not cover the age group of 5–11 years, there is no significant change in hospitalization rates in this age group. In conclusion, this study emphasizes that the proportion of children younger than 1-year-old among hospitalized children with COVID-19 infection during the Omicron era is alarming for pediatricians.