ABSTRACT
BackgroundPost-acute symptoms are not uncommon after SARS-CoV-2 infection with pre-Omicron variants. How the Omicron variant and COVID-19 booster vaccination influences the risk of post-acute symptoms is less clear. ObjectivesTo evaluate the effects of the Omicron variant and COVID-19 booster vaccination on post-acute symptoms, four months after infection with SARS-CoV-2. MethodsA nationwide Danish questionnaire study comprising 44,004 individuals aged 15 years or older with outcomes on post-acute symptoms and new-onset general health problems, four months after testing. 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. ResultsFour months after testing for SARS-CoV-2 during the Omicron period, the largest RD comparing Omicron cases to controls was observed for memory issues (RD=7.2%, 95% CI: 6.4 to 8.1). Compared to cases from the Delta period, Omicron cases reported reduced risks of post-acute dysosmia (RD=-15.5%, 95% CI: -17.5 to -13.4) and dysgeusia (RD=-11.8%, 95% CI: -13.9 to -9.8). Cases vaccinated with three doses prior to Omicron infection reported reduced risk of 13/26 post-acute symptoms and of 4/5 new-onset general health problems, compared to those vaccinated with two doses. ConclusionsCases infected during the Omicron period experienced substantial post-acute symptoms and new-onset health problems, four months after testing, although milder than Delta cases. Booster vaccination was associated with fewer post-acute symptoms and new-onset health problems, four months after Omicron infection, compared to two doses of COVID-19 vaccine.
