Duration of mild acute SARS-CoV-2 infections with Omicron depending on previous vaccinations and infections : using data of the German DigiHero cohort study from post-pandemic winters 2022/2023 and 2023/2024

Abstract

Objectives: Protection against severe course of SARS-CoV-2 infection after COVID-19 vaccination or infec tion was extensively studied. It is unknown whether this effect also translates into shortened duration of mild infections. We assessed the duration of symptoms depending on vaccination status and previous SARS- CoV-2 infections among individuals with a mild course of infection. Methods: For two post-pandemic winters (2022/2023 and 2023/2024), in total 13,615 participants of the German DigiHero study reported their SARS-CoV-2 infections from September to March. Via negative bi nomial regression adjusting for sociodemographic factors, we studied the association of infection duration (days with symptoms and in bed) with number of vaccinations, prior SARS-CoV-2 infections, and time since last vaccination/and infection. Results: We noted no major differences in infection duration depending on the number of vaccinations and time since last infection for short mild infections (≤21 days with symptoms). Per 6 months since the last vaccination, symptom duration and days spent in bed increased by 2 % and 4 %. The risk of long mild SARS-CoV- 2 infections (> 21 days with symptoms) was higher for individuals with no prior SARS-CoV-2 infection (Odds Ratio: 1.98; 95 % confidence interval [1.43; 2.76]), but not for vaccinations (OR: 0.98; 95 % CI [0.74; 1.33]). Conclusions: There was no indication of reduced duration of symptoms during short mild infections de pending on the number of vaccinations and time since the last SARS-CoV-2 vaccination or infection. A prior SARS-CoV-2 infection was protective against prolonged disease in mild SARS-CoV-2 infections.