Cohort profile: The Corona Behavioral Unit cohort, a longitudinal mixed-methods study on COVID-19-related behavior, well-being and policy support in the Netherlands

Abstract

This 'cohort profile' aims to provide a description of the study design, methodology, and baseline characteristics of the participants in the Corona Behavioral Unit cohort. This cohort was established in response to the COVID-19 pandemic by the Dutch National Institute for Public Health and the Environment (RIVM) and the regional public health services. The aim was to investigate adherence of and support for COVID-19 prevention measures, psychosocial determinants of COVID-19 behaviors, well-being, COVID-19 vaccination, and media use. The cohort also examined specific motivations and beliefs, such as for vaccination, which were collected through either closed-ended items or open text responses. In April 2020, 89,943 participants aged 16 years and older were recruited from existing nation-wide panels. Between May 2020 and September 2022, 99,676 additional participants were recruited through online social media platforms and mailing lists of higher education organizations. Participants who consented were initially invited every three weeks (5 rounds), then every six weeks (13 rounds), and since the summer of 2022 every 12 weeks (3 rounds). To date, 66% of participants were female, 30% were 39 years and younger, and 54% completed two or more questionnaires, with an average of 9.2 (SD = 5.7) questionnaires. The Corona Behavioral Unit COVID-19 cohort has published detailed insights into longitudinal patterns of COVID-19 related behaviors, support of COVID-19 preventive measures, as well as peoples' mental wellbeing in relation to the stringency of these measures. The results have informed COVID-19 policy making and pandemic communication in the Netherlands throughout the COVID-19 pandemic. The cohort data will continuously be used to examine COVID-19 related outcomes for scientific analyses, as well as to inform future pandemic preparedness plans.

Fig 1. Questionnaire modules in baseline and follow up questionnaires, Corona Behavioral Unit cohort study, April 2020 –September 2022.

In follow-up questionnaires, all participants filled out a short version of the sociodemographic module with items that could potentially have changed over time (eg, medical health condition), that were needed for linkage purposes (i.e., age and sex–see more details below), were included for routing purposes (eg, having kids for questions related to kids), or were related to COVID-19 vaccination, testing and infection. Also, all participants filled out questions from the behavior module, and, based on the baseline module and random allocation during follow-up, was complemented with questions from a module on either (d) psychosocial determinants of adherence, (e) policy support, use of media and trust in the COVID-19 approach of the Dutch government, or (f) well-being, use of media and trust in the COVID-19 approach of the Dutch government (Fig 1).

Fig 2. Flow diagram Corona Behavioral Unit cohort study, April 2020 –September 2022.

¹ Other reasons for uncompleted questionnaires are: open link had been used more than once, email address was not correct, survey was closed because participant’s age was below the minimum, participant did not give permission to use their data. ² Participant id number, age and sex from the baseline questionnaires were used to match participants on their follow-up questionnaires.