The representative COVID-19 cohort Munich (KoCo19): from the beginning of the pandemic to the Delta virus variant.

Publication date: Jul 13, 2023

Population-based serological studies allow to estimate prevalence of SARS-CoV-2 infections despite a substantial number of mild or asymptomatic disease courses. This became even more relevant for decision making after vaccination started. The KoCo19 cohort tracks the pandemic progress in the Munich general population for over two years, setting it apart in Europe. Recruitment occurred during the initial pandemic wave, including 5313 participants above 13 years from private households in Munich. Four follow-ups were held at crucial times of the pandemic, with response rates of at least 70%. Participants filled questionnaires on socio-demographics and potential risk factors of infection. From Follow-up 2, information on SARS-CoV-2 vaccination was added. SARS-CoV-2 antibody status was measured using the Roche Elecsys(R) Anti-SARS-CoV-2 anti-N assay (indicating previous infection) and the Roche Elecsys(R) Anti-SARS-CoV-2 anti-S assay (indicating previous infection and/or vaccination). This allowed us to distinguish between sources of acquired antibodies. The SARS-CoV-2 estimated cumulative sero-prevalence increased from 1. 6% (1. 1-2. 1%) in May 2020 to 14. 5% (12. 7-16. 2%) in November 2021. Underreporting with respect to official numbers fluctuated with testing policies and capacities, becoming a factor of more than two during the second half of 2021. Simultaneously, the vaccination campaign against the SARS-CoV-2 virus increased the percentage of the Munich population having antibodies, with 86. 8% (85. 5-87. 9%) having developed anti-S and/or anti-N in November 2021. Incidence rates for infections after (BTI) and without previous vaccination (INS) differed (ratio INS/BTI of 2. 1, 0. 7-3. 6). However, the prevalence of infections was higher in the non-vaccinated population than in the vaccinated one. Considering the whole follow-up time, being born outside Germany, working in a high-risk job and living area per inhabitant were identified as risk factors for infection, while other socio-demographic and health-related variables were not. Although we obtained significant within-household clustering of SARS-CoV-2 cases, no further geospatial clustering was found. Vaccination increased the coverage of the Munich population presenting SARS-CoV-2 antibodies, but breakthrough infections contribute to community spread. As underreporting stays relevant over time, infections can go undetected, so non-pharmaceutical measures are crucial, particularly for highly contagious strains like Omicron.

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Concepts Keywords
Asymptomatic Breakthrough infections
Geospatial COVID-19
November Population-based cohort study
Vaccines SARS-CoV-2
Vaccination status


Type Source Name
disease MESH COVID-19
disease VO population
disease MESH asymptomatic disease
disease VO vaccination
disease MESH infection
disease IDO assay
disease VO vaccinated
disease VO time
disease MESH breakthrough infections
disease MESH Infectious Diseases
pathway REACTOME Reproduction
disease IDO blood
drug DRUGBANK Polyethylene glycol
disease VO effective
disease IDO contact tracing
disease MESH emergency
disease IDO country
disease MESH chronic conditions
disease VO vaccine
drug DRUGBANK Aspartame
disease IDO symptom
disease MESH reinfections
drug DRUGBANK Hyaluronic acid
disease MESH uncertainty
disease IDO process
drug DRUGBANK Coenzyme M
disease MESH allergies
disease MESH Obesity
disease MESH asymptomatic infections
drug DRUGBANK Indoleacetic acid
disease IDO facility
drug DRUGBANK Esomeprazole
disease MESH long COVID
drug DRUGBANK Etoperidone
drug DRUGBANK Trestolone
drug DRUGBANK Cinnarizine
disease VO storage
disease VO protocol
disease IDO site
disease VO organization
drug DRUGBANK Hydroxyethyl Starch
drug DRUGBANK Huperzine B
disease VO effectiveness
drug DRUGBANK Diethylstilbestrol
drug DRUGBANK Gold
disease MESH Amelia
disease IDO primary infection
disease VO unvaccinated
disease VO vaccine effectiveness
disease MESH Breakthrough infections COVID-19

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