Attitudes towards booster, testing and isolation, and their impact on COVID-19 response in winter 2022/2023 in France, Belgium, and Italy

European countries are focusing on testing, isolation, and boosting strategies to counter the 2022/2023 winter surge due to Omicron subvariants. However, widespread pandemic fatigue and limited compliance potentially undermine mitigation efforts. To establish a baseline for interventions, we ran a multicountry survey to assess respondents’ willingness to receive booster vaccination and comply with testing and isolation mandates. The vast majority of survey participants (N=4,594) was willing to adhere to testing (>91%) and rapid isolation (>88%) across the three countries. Pronounced differences emerged in the declared senior adherence to booster vaccination (73% in France, 94% in Belgium, 86% in Italy). Next, we inferred the vaccine-induced population immunity profile at the winter start from prior vaccination data, immunity waning, and declared booster uptake. Integrating survey and estimated immunity data in a branching process epidemic spreading model, we evaluated the effectiveness and costs of current protocols in France, Belgium, and Italy to manage the winter wave. Model results estimate that testing and isolation protocols would confer significant benefit in reducing transmission (17-24%) with declared adherence. Achieving a mitigating level similar to the French protocol, the Belgian protocol would require 30% fewer tests and avoid the long isolation periods of the Italian protocol (average of 6 days vs. 11). A cost barrier to test would significantly decrease adherence in France and Belgium, undermining protocols’ effectiveness. Simpler mandates for isolation may increase awareness and actual compliance, reducing testing costs, without compromising mitigation. High booster vaccination uptake remains key for the control of the winter wave. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was partly supported by: Agence Nationale de la Recherche projects COSCREEN (ANR-21-CO16-0005) and DATAREDUX (ANR-19-CE46-0008-03) to VC; ANRS-Maladies Infectieuses Émergentes project EMERGEN (ANRS0151) to VC; EU Horizon 2020 grants MOOD (H2020-874850) and RECOVER (H2020-101003589) to VC, EpiPose (101003688) to DP, LH, NH; Horizon Europe VERDI (101045989) to VC, DP; the Chaire Blaise Pascal Program of the Île-de-France region to JSW. Views and opinions expressed are those of the authors and do not necessarily reflect those of the funding agencies and authorities, who cannot be held responsible for them. ### 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 French Advisory Committee for research on information treatment in the health sector (CCTIRS), and the French National Commission on Informatics and Liberty (CNIL) gave ethical approval for this work regarding GrippeNet.fr/COVIDnet.fr. The Committee for Medical Ethics of Antwerp University (EC UZA-UA) gave ethical approval for this work regarding Infectieradar.be. The IRB of ISI Foundation waived ethical approval for this work regarding Influweb.it. 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 and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes Survey individual data cannot be shared owing to restrictions imposed by the national data protection authorities. Stratified data on survey responses will be made available in a persistent repository upon publication.