Risk factors for SARS-CoV-2 infection and hospitalisation in children and adolescents in Norway: a nationwide population-based study

Abstract

Objective: To determine risk factors for SARS-CoV-2 infection and hospitalisation among children and adolescents.

Design: Nationwide, population-based cohort study.

Setting: Norway from 1 March 2020 to 30 November 2021.

Participants: All Norwegian residents<18 years of age.

Main outcome measures: Population-based healthcare and population registries were used to study risk factors for SARS-CoV-2 infection, including socioeconomic factors, country of origin and pre-existing chronic comorbidities. All residents were followed until age 18 years, emigration, death or end of follow-up. HRs estimated by Cox regression models were adjusted for testing frequency. Further, risk factors for admission to the hospital among the infected were investigated.

Results: Of 1 219 184 residents, 82 734 (6.7%) tested positive by PCR or lateral flow tests, of whom 241 (0.29%) were admitted to a hospital. Low family income (adjusted HR (aHR) 1.26, 95% CI 1.23 to 1.30), crowded housing (1.27, 1.24 to 1.30), household size, age, non-Nordic country of origin (1.63, 1.60 to 1.66) and area of living were independent risk factors for infection. Chronic comorbidity was associated with a slightly lower risk of infection (aHR 0.90, 95% CI 0.88 to 0.93). Chronic comorbidity was associated with hospitalisation (aHR 3.46, 95% CI 2.50 to 4.80), in addition to age, whereas socioeconomic status and country of origin did not predict hospitalisation among those infected.

Conclusions: Socioeconomic factors, country of origin and area of living were associated with the risk of SARS-CoV-2 infection. However, these factors did not predict hospitalisation among those infected. Chronic comorbidity was associated with higher risk of admission but slightly lower overall risk of acquiring SARS-CoV-2.

Keywords: COVID-19; SARS-CoV-2; comorbidity; country of origin; hospitalisation; risk factor; socioeconomy.

Figure 1

Flow of data and data sources for BEREDT C19. ICE-10, International Classification of Diseases; ICPC-2, International Classification for Primary Care.

Figure 2

Pre-existing chronic condition in the population and in those infected with SARS-CoV-2 and adjusted HR for infection^*. ^*Adjusted for age, sex, region, municipality size, household size, household crowding, low family income, testing frequency and country of origin. aHR, adjusted HR.

Figure 3

Age at time of positive test and sex of infected with SARS-CoV-2 (cumulative cases from 1 March 2020 to 30 November 2021).