This data collection includes quantitative and interview data obtained in the three research strands of this project. STRAND 1 is comprised of 17 studies: two survey studies and 15 experimental studies. STRAND 2 is comprised of three studies: two interview studies, and one quantitative survey study. STRAND 3 included an interview study, whose data includes sensitive personally identifying information. Consent for publicly sharing the interview study data is not in place and retrospective consent is not feasible, and accordingly a waiver has been granted for these data.There is international recognition that effective response to Covid-19 is dependent upon the public acting collectively and for the common good. This is important in terms of adherence to preventative measures, which, especially for low-risk groups, is as much about protecting others as protecting oneself. It is important in terms of volunteering and mutual aid, which is critical in complementing the official response by supporting and sustaining people through the pandemic. It is also important in terms of maintaining social cohesion and avoiding social disorder. This multi-method project builds upon understandings of psychological group processes to address how to develop and sustain shared identity and social solidarity during pandemics. It is organised around three interrelated strands that together address the issues of adherence, mutual aid and social order. The first strand uses experiments to examine the impact of collective identification on adherence, the role of leadership in developing collective identification, and how coverage of others' positive or negative behaviours (e.g., volunteering vs. stockpiling) impacts collective identity and adherence to preventative measures. The second strand uses interview and survey methods to understand why people join emergent mutual aid groups, the effects of participation upon efficacy and well-being, and how such groups can be sustained over time. The third strand uses ethnographic interviews to examine the UK's security and civil contingency response to the pandemic and enforcement data to understand how responder actions impact upon community relations, adherence and social tensions.

Strand 1 All study data was collected using Prolific (https://www.prolific.co/). Sample, payment, and dates for data collection for each study are given below. Preventative measures survey study: 103 UK-based adult respondents (71 female, 32 male; mean age 35.8, range 18-71), each paid £1, data collected 3 Nov 2020. Risk survey study: 300 UK-based adult respondants (186 female, 110 male, 4 other/undisclosed gender; mean age 51.4, range 18-88), each paid £1, data collected 24-27 Nov 2020. Risk experimental study 1: 199 UK-based adult participants (142 female, 54 male, 3 other/undisclosed gender; age 18-89, mean 33), each paid £2, data collected 27 May 2021. Risk experimental study 2: 553 UK-based adult participants (383 female, 166 male, 4 other/undisclosedgender; age 18–88, mean 43), each paid £2, data collected 20 Sept 2021. Vaccine nationalism study 1: 678 British UK-based adult participants (438 female, 229 male, 11other/undisclosed gender; age 18-75, mean 34.2), each paid £1, data collected 25-27 Jan 2021. Vaccine nationalism study 2: 498 British UK-based adult participants (319 female, 178 male, 1other/undisclosed gender; age 18-83, mean 33.8), each paid £1, data collected 10 Feb 2021. Self isolation study 1: 300 UK-based adult participants (212 female, 85 male, and 3 other; aged 18-75, mean 32.6), each paid £1.50, data collected 19 Feb 2021. Self isolation study 2: 402 UK-based adult participants (276 female, 125 male, and 1 non-binary; aged 18-72, mean 33.5), each paid £1.50, data collected 2 March 2021. Self isolation study 3: 300 UK-based adult participants (183 female, 114 male, and 3-non-binary; aged 18-75, mean 36.8) who had had COVID-19, each paid £1.50, data collected 5-8 March 2021. Self isolation study 4: 588 UK-based adult participants (480 female, 289 male, 10 other, and 3 who did not provide their gender; age 18–74, mean 32.2), each paid £2, data collected 1-2 Sept 2021. Physical distancing paper 1 study 1: 197 English UK-based adult participants(118 female, 76 male, 3 other/undisclosed gender; age 18-80, mean 34.8), each paid £2, data collected 17-18 June 2021. Physical distancing paper 1 study 2: 198 English UK-based adult participants (114female, 77 male, 7 other/undisclosed gender; age 18-65, mean 27.6), each paid £2, data collected 29 June 2021. Physical distancing paper 2 study 1: 401 English UK-based adult participants (258 female, 131 male, 12 other/undisclosedgender; age 18-72, mean 30.0), each paid £2, data collected 2-3 July 2021. Physical distancing paper 2 study 2: 398 English UK-based adult participants (253 female, 137 male, 8 other/undisclosed gender;age 18-80, mean 31.5), each paid £2, data collected 6-7 July 2021. Physical distancing paper 3 study 1: 400 English UK-based adult participants (283 female, 112 male, 5 other/undisclosed gender; age 18-72, mean 32.7), each paid £2, data collected 7 July 2021. Physical distancing paper 3 study 2: 560 English UK-based adult participants (339 female, 214 male, 6 other/undisclosed gender; age 18-73, mean 31.5), each paid £2, data collected 9-10 July 2021. Physical distancing paper 3 study 3: 395 English UK-based adult participants (229 female, 155 male,11 other/undisclosed gender; age 18–68, mean 33.0), each paid £2, data collected 9-10 July 2021. Strand 2 1. Interview studies Interview study 1: “Mutual Aid and Wellbeing” The criteria for inclusion in the study was participation in ACORN’s Coronavirus Community Support initiative. We sought to recruit a sample that was relatively homogeneous and small, to allow us to examine the shared experiences of a particular group in depth. We determined a target sample size of 12 prior to sample collection. Participants were recruited via several methods: personal contacts ofthe first author, advertising via social media groups, and approaching individuals who had been active on ACORN’s organizing spreadsheet. As thanks, participants could vote for one of three charities to receive a share of a £25 donation. Fifteen individuals responded to our initial recruitment methods: of these, four dropped off after further contact and eleven were interviewed. Participants had engaged in various activities:.managing the support line; organizing volunteers; delivering shopping, money, and prescriptions; and volunteering for allied organizations. Additionally, one participant (P2) had been involved in setting up their own local mutual aid network. All participants but one described joining the Community Support initiative fromwhen it began in early April, soon after the first UK lockdown was announced on March 23; the remaining participant (P5) joined at the beginning of June. Levels of participation ranged from 2 h total to 25 h a week. Interview study 2: “Sustaining Community Solidarity” Thirty-two semi-structured interviews were conducted between 10 September 2020 and 6 January 2021. Participants were approximately between 20 and 75 years old, 17 were female and 15 male. All were organizers rather than simply volunteers in mutual aid groups. Twenty-four interviewees were coordinators of mutual aid or community support groups in England, four in Wales, three in Scotland, and one in North Ireland. Participants were recruited through multiple channels. A call for participants was disseminated through diverse networks (e.g., the Communities Prepared program) and social media accounts (e.g., professional and personal Twitter accounts). The call for participants stated that we wanted to interview organizers of COVID-19 mutual aid or community support groups. We also directly contacted mutual aid groups across the country with an invitation to participate in the study. These groups had their email addresses publicly available and were identified through searches on Facebook and national networks of mutual aid groups (e.g., COVID-19 Mutual Aid United Kingdom). We approached both pre-existing and emergent groups and we sought variability in terms of geographic location, areas of intervention (e.g., shopping groceries; helpline support), and socio-demographic characteristics of the participants. Mutual aid groups were invited to share their experiences and views on the factors that enable mutual aid groups to endure. If groups showed interest in participating, more details about the study were provided in a detailed participant information sheet. We interviewed one participant per group, except for three groups for which two organizers were interviewed from each. Therefore, we spoke to organizers from 29 different groups. A few interviewees also mentioned being involved in more than one group (including in pre- existing and emergent groups), although they ended up focusing the interview on the group they were more strongly engaged with. Potential participants were asked to give written informed consent. We offered a £20 voucher as compensation for participants’ time. 2. Quantitative survey Participants were 600 UK residents who had taken part in community groups to support people locally during the Covid-19 pandemic. At Wave 1, participants were aged 18-75 (Mage = 45.41, SDage = 15.86), 50% female, 45% employed full-time, 38% educated to NVQ3/SCE Higher Grade/Advanced GNVQ/GCE A/AS or similar, and 84% reported White as their ethnic group. Participants were registered panellists of an independent research agency commissioned for this project (Ipsos MORI). At Wave 1, data was weighted to the known offline population proportions for age and working status within gender and government office region. Strand 3 included an interview study, whose data includes sensitive personally identifying information. Consent for publicly sharing the interview study data is not in place and retrospective consent is not feasible, and accordingly a waiver has been granted for these data.