Head of Unit at ARS Toscana, Florence, Italy ARS Toscana, Florence, Italy Florence, Italy
Background: Children were less affected by COVID-19 at the start of the pandemic. Little is known about the severity of COVID-19 infection in children on a population level.
Objectives: To estimate the incidence rate (IR) of SARS-CoV-2 infections stratified by severity and vaccine intake in the general paediatric population.
Methods: Multi-database cohort study using data from 6 Italian and Spanish population-based electronic healthcare records databases. The study period started the 1st of January 2020 until the latest data available for each data source. SARS-CoV-2 infections were obtained from PCR or antigen tests, or diagnosis codes. Four COVID-19 severity levels were distinguished: 1) without hospitalization (non-severe), 2) hospitalization, 3) intensive care unit admission, and 4) death. Incidence rates (IRs per 100,000 person-years (PY)) and exact 95% confidence intervals for COVID-19 disease severity levels were estimated prior to vaccination and after the first dose (excluding days 0-7 after vaccination).
Results: The total study population comprised 4,447,460 children 0-18 years of age (54% women), median age 6-9 years across the 6 databases. In Italian databases, the peak of COVID-19 infections was in December 2021 and January 2022. In children 5-11 years, the incidence rate of non-severe COVID-19 disease was highest in December 2021-January 2022: 85,214-248,087/100,000 PY. In 12 to 18-year-olds, the incidence rate of non-severe COVID-19 ranged between 41,495-162,869/100,000 PY (December 2021 and January 2022, respectively). In Spanish databases, the peak of non-severe COVID-19 infection in children from 5- < 12 years-old was 84,334-154,083/100,000 PY in December 2021-January 2022. In adolescents, the highest rates of non-complicated COVID-19 were from 74,506-154,000/100,000 PY. Severe cases of COVID-19 infection in the Spanish general population 0-18 years accounted for less than 0.9% of the cases whereas, in Italy, from 0.2 to 2.6% across data sources. Comirnaty (Pfizer-BioNTech) was the most administered 1st dose vaccine brand followed by Spikevax (9-20%). Non-adjusted rates of COVID-19 dropped substantially one week after vaccination in all the data sources.
Conclusions: Incidence rates of non-severe paediatric COVID-19 infection reached the highest level in December 2021 and January 2022, aligned with the Omicron peak. Severe cases of COVID-19 were low in children. Post-vaccination crude infection rates were very low.
.jpg "Rosa Gini, PhD (she/her/hers) photo")
