The impact of COVID-19 vaccination campaigns accounting for antibody-dependent enhancement Nessma Adil M. Y. 1,2 , H. Christian Jr. Tsoungui Obama 1,2 , Jordan Y. Ngucho 2 , S. Frank Kwamou 1,2 , Loyce Kayanula 1,2 , George Kamanga 1,2 , Toheeb B. Ibrahim 1,2 , Patience Bwanu Iliya 1,2 , Sulyman Iyanda 1,2 , Looli Alawam 1,2 , Miranda I. Teboh-Ewungkem 3 , Kristan A. Schneider 1* 1 Department of Applied Computer- and Biosciences, University of Applied Sciences Mittweida, Mittweida, Germany 2 African Institute for Mathematical Sciences Cameroon, Limbe, Cameroon 3 Department of Mathematics, Lehigh University, Bethlehem, PA, USA These authors contributed equally to this work. *kristan.schneider@hs-mittweida.de Abstract Background: COVID-19 vaccines are approved, vaccination campaigns are launched, and worldwide return to normality seems within close reach. Nevertheless, concerns about the safety of COVID-19 vaccines arose, due to their fast emergency approval. In fact, the problem of antibody-dependent enhancement was raised in the context of COVID-19 vaccines. Methods and findings: We introduce a complex extension of the model underlying the pandemic preparedness tool CovidSim 1.1 (http://covidsim.eu/) to optimize vaccination strategies with regard to the onset of campaigns, vaccination coverage, vaccination schedules, vaccination rates, and efficiency of vaccines. Vaccines are not assumed to immunize perfectly. Some individuals fail to immunize, some reach only partial immunity, and – importantly – some develop antibody-dependent enhancement, which increases the likelihood of developing symptomatic and severe episodes (associated with higher case fatality) upon infection. Only a fraction of the population will be vaccinated, reflecting vaccination hesitancy or contraindications. We parameterized the model to reflect the situation in Germany and predict increasing incidence (and prevalence) in early 2021 followed by a decline by summer. Assuming contact reductions (curfews, social distancing, etc.) to be lifted in summer, disease incidence will peak again. Fast vaccine deployment contributes to reduce disease incidence in the first quarter of 2021, and delay the epidemic outbreak after the summer season. Higher vaccination coverage results in a delayed and reduced epidemic peak. A coverage of 75% - 80% is necessary to prevent an epidemic peak without further drastic contact reductions. Conclusions: With the vaccine becoming available, compliance with contact reductions is likely to fade. To prevent further economic damage from COVID-19, high levels of immunization need to be reached before next year’s flu season, and vaccination strategies and disease management need to be flexibly adjusted. The predictive model can serve as a refined decision support tool for COVID-19 management. December 29, 2020 1/14 . CC-BY 4.0 International license available under a (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made The copyright holder for this preprint this version posted January 4, 2021. ; https://doi.org/10.1101/2021.01.04.425198 doi: bioRxiv preprint