Contact behaviour before, during and after the COVID-19 pandemic in the Netherlands: evidence from contact surveys in 2016-2017 and 2020-2023

Background The first wave of the COVID-19 pandemic in 2020 was largely mitigated by reducing contacts in the general population. In 2022 most contact-reducing measures were lifted. Aim We assess whether the population has reverted to pre-pandemic contact behaviour and how this would affect the transmission potential of a newly emerging pathogen. Methods The PIENTER Corona study was held every 2-6 months in the Netherlands from April 2020, as a follow-up on the 2016-2017 PIENTER3 study. In both studies, participants (ages 1-85) reported the number and age group of all face-to-face persons contacted on the previous day. The contact behaviour during and after the COVID-19 pandemic was compared to the pre-pandemic baseline. Results We found an average of 15.2 (13.3-16.9, 95% CI) community contacts per person per day in the post-pandemic period, which is 14% lower than the baseline value of 17.6 (16.3-18.9). Children have the highest number of contacts as before the pandemic. Mainly adults aged 20-59 have not reverted to their pre-pandemic behaviour, possibly because this age group works more often from home. Although the number of contacts is structurally lower compared to the pre-pandemic period, the effect on the potential spread of a newly emerging respiratory pathogen is limited if all age groups were equally susceptible. If younger age groups were less susceptible, as observed during the first COVID-19 wave, the transmission potential as well as the required control effort would be lower. Conclusion Continuous monitoring of contacts is needed to be prepared for a future pandemic. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This study was funded by the Ministry of Health, Welfare and Sport (VWS) in the Netherlands. The authors of this study (JB and JW) received funding from European Union's Horizon 2020 research and innovation programme - projects EpiPose (Grant agreement number 101003688) and ESCAPE (Grant agreement number 101095619). ### 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 Medical Research Ethics Committees United (MEC-U) in the Netherlands approved the study, conformed to the principles embodied in the Declaration of Helsinki, and all participants provided written informed consent. 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 The cleaned data are available online at