Post-acute symptoms 4 months after SARS-CoV-2 infection during the Omicron period: a nationwide Danish questionnaire study.

ABSTRACT

Post-acute symptoms are not uncommon after SARS-CoV-2 infection with pre-Omicron variants. How Omicron and COVID-19 booster vaccination influence the risk of post-acute symptoms is less clear. We analyzed data from the nationwide Danish questionnaire study EFTER-COVID comprising 44,553 individuals ≥15 years old, tested between July 2021 and January 2022, in order to evaluate the association of the Omicron variant and COVID-19 booster vaccination with post-acute symptoms and new-onset general health problems, four months after infection with SARS-CoV-2. Risk differences (RDs) were estimated by comparing Omicron -cases to controls, Omicron to Delta -cases, and Omicron vaccinated cases with three to -two doses, adjusted for age, sex, BMI, self-reported chronic diseases, Charlson comorbidity index, healthcare occupation, and vaccination status. Four months after testing for SARS-CoV-2 during the Omicron period, cases experienced substantial post-acute symptoms and new-onset health problems compared to controls; the largest RD was observed for memory issues (RD=7.2%, 95%CI 6.4 to 8.1). However, risks were generally lower than in the Delta period, particularly for dysosmia (RD=-15.0%, 95%CI -17.0 to -13.2) and dysgeusia (RD=-11.2%, 95%CI -13.2 to -9.5). Booster vaccination was associated with fewer post-acute symptoms and new-onset health problems, four months after Omicron infection, compared to two COVID-19 vaccine doses.