社会活動は感染件数の40～60％を説明、公共交通機関は感染拡大に大きく寄与

We developed a state-space model to investigate which social behaviours had biggest impact on the spread of SARS-CoV-2. The analyses were based on reported hospitalizations, together with information on vaccinations, weather data, virus strains and, most importantly, Google mobility reports on 4 different types of social activities. While our new approach is general, we studied Sweden and Norway on a regional level over 75 weeks, and the major regions of Berlin and Bavaria in Germany over 10 months. Most results are shared for all three countries: Activity in four social settings explain between 40-60% of all infections; Public transport appears as an important setting for infections in all countries; and the transmission potential drops by 40-50% during the summer as compared to the winter peak. However, the analyses for Germany differ in that Retail and recreation is the other setting dominating transmission whereas it is contacts at the Workplace in Norway and Sweden, showing how our model is able to adapt to specific cases. Transmissions not captured by the Google data may happen in other settings, in particular in households. The statistical model has a deterministic time and region specific transmission rate with an additive component for the four Google settings, and a multiplicative part taking seasonality and circulating virus strains into account. Inference is performed in a Bayesian setting using Stan. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by the Nordforsk project 105572. AF and HKB were also supported by BigInsight, the Norwegian Research Council project number 237718. AF was also supported by Integreat, the Norwegian Research Council project number 332645. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study used publicly available data on the number the number of Covid-19 hospitalizations, vaccination numbers, and share of virus variants as provided by the Public health agencies of the considered countries (Sweden, Norway, and Germany). The finest level of aggregation was weekly (cumulative) numbers at county/federal state level. Data was obtained from the following web ressources: https://www.fhi.no/en/id/corona/coronavirus/daily-reports/daily-reports-COVID19/Data https://www.socialstyrelsen.se/statistik-och-data/statistik/statistik-om-covid-19/ https://github.com/robert-koch-institut/COVID-19-Hospitalisierungen\_in\_Deutschland/ I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors. Code and data for a central part of the analysis are available at: https://github.com/FelixGuenther/nordic\_behavior\_public/ Publicly available data on COVID-19 hospitalization counts were obtained from NOR: https://www.fhi.no/en/id/corona/coronavirus/daily-reports/daily-reports-COVID19/Data SWE: https://www.socialstyrelsen.se/statistik-och-data/statistik/statistik-om-covid-19/ GER: https://github.com/robert-koch-institut/COVID-19-Hospitalisierungen\_in\_Deutschland/ [https://github.com/FelixGuenther/nordic\_behavior\_public/][1] [1]: https://github.com/FelixGuenther/nordic_behavior_public/