ABSTRACT
OBJECTIVES: Omicron appears to lead to a milder illness for patients compared with previous COVID-19 variants. However, not all infected with Omicron would describe their illness as mild. In this study, we investigate the experienced severity and symptoms of the Omicron variant. METHODS: We conducted a nationwide cross-sectional study, including 5036 individuals of all ages, consisting of reverse transcription-polymerase chain reaction confirmed SARS-CoV-2 cases from 1 January to 31 January 2022 (n = 4506) and a control group without SARS-COV-2 infection in December 2021 or January 2022 (n = 530). Omicron was dominant during this period. Cases were asked about their acute symptoms and answered a web-based questionnaire 10-30 days after their positive test while controls were asked about symptoms during the past week. RESULTS: Among cases, 97% reported at least one symptom during the acute phase compared with 79% of controls. Just over half the cases assessed their illness as asymptomatic or mild, whereas 46% assessed their illness as moderate or severe. Children reported fewer symptoms and less severe illnesses than adults (P <0.001). The largest risk differences (RDs) between adult cases and controls due to symptoms were observed for fever (RD = 60.6%, confidence interval [CI] 57.4-63.6), fatigue (RD = 49.6%, CI 44.1-54.7), and chills (RD = 48.8%, CI 43.8-53.2). CONCLUSION: Most of those infected with Omicron experience symptoms, and the Omicron variant appears to lead to less severe disease. However, this does not mean that all the infected experience an Omicron infection as mild. The unprecedented rate of Omicron infections worldwide leads to urgent questions about the rate of long COVID after Omicron infections.