With the Omicron variant of covid infections among the smallest are soaring. The confirmation comes from a study published in the journal ‘Jama Pediatrics’ and conducted in the US on 650 thousand children: among the under 5s, the incidence rate of infection in the Omicron era was 6 to 8 times that recorded with Delta. The work is signed by researchers from Case Western Reserve University School of Medicine (Ohio), MetroHealth System (Cleveland, Ohio) and National Institute on Drug Abuse (Nih) in Bethesda, Maryland. It also shows how the risks for serious clinical outcomes in children infected with the Omicron variant were significantly lower than those seen in the Delta cohort.
The study population was divided into 3 cohorts of under 5 with no previous Sars-CoV-2 infection: the Omicron cohort, made up of children who contracted Sars-CoV-2 infection between 26 December 2021 and 25 January 2022; the Delta cohort (B.1.617.2), made up of children infected between 1 September 2021 and 15 November 2021; and the Delta 2 cohort, of infected between November 16 and November 30, 2021. The monthly incidence rate of infections remained mostly stable (1.0-1.5 cases per 1,000 people per day) between September and November 2021 (Delta prevalence period), but it has rapidly increased – explain Lindsey Wang and colleagues – to 2.4-5.6 cases per 1,000 people per day in December 2021, coinciding with the emergence of the Omicron variant.
The monthly incidence rate of infections among children under the age of 5 then peaked at 8.6 cases per 1,000 people per day in the first half of January 2022 (Omicron prevalence period) and 8.2 in the second half. of the same month. The incidence of Omicron contagion was higher in 0-2 year olds than in 3 to 4 year olds. There were fewer than 10 deaths in all cohorts. And with Omicron, the authors confirm, severe cases were less frequent than with the Delta variant.