Perceptions of vaccination certificates among the general population in Geneva, Switzerland

DOI: https://doi.org/10.4414/SMW.2021.w30079

Introduction

The COVID-19 pandemic will continue to have an impact on several dimensions of physical and mental health, as well as on social and economic parameters for years to come [1–3]. With the advent of effective vaccines, mass vaccination is recognised as a way out of the pandemic, especially when it is taken into account that any public health restrictive measures should be an adequate response to specific and demonstrable risk [4, 5]. Countries with extensive vaccination programmes have already implemented “green passes”, and the European Union deployed COVID certificates [6], in an effort to resume and once again allow free movement. Switzerland’s COVID certificates have been available since June 2021. COVID certificates can attest to an individual’s vaccination status, a past SARS-CoV-2 infection or the absence of current infection [7]. As of September 2021, COVID certificates in Switzerland are used for indoor events, discos and dance events, indoor areas of bars and restaurants, cultural sporting and recreational facilities, international travel, and large gatherings of at least 1,000 individuals [7].

Implementation is underway, but little is known about the public perception of COVID certificates. There has been conflicting evidence about the role of COVID certificates in vaccination programme uptake and as a strategy in a phased reduction of lockdown measures [8, 9]. Vaccination certificates could allow safer access to several activities, and may increase the uptake of immunisation when an incentive-based approach is considered [10, 11]. However, they could also be viewed as coercive measures creating a backlash and further increasing any pre-existing resistance to vaccination [10, 12, 13]. A recent review of the public perception of COVID certificates, their potential impact on behaviour, and the uptake of testing and vaccination reported different acceptance rates depending on context (travel, social or professional) [14]. There was little information on sociodemographic differences in most of the studies included in this review [14]. A survey addressed to 12,000 scientists revealed their overall favourable attitudes towards COVID certificates [15]. Scientists perceived immunity certificates favourably for their positive impact on public health and the economy, despite highlighting risks related to equity and equality of the implementation process. Differences were perceived among participants as US-based scholars, men and scientists with more conservative political views were overall more favourable to immunity certificates [15].

To date, there is little information about the general population-based acceptance and perception of COVID certificates. In November 2020 [16], we published results on the perception of immunity certificates, mostly in relation to natural immunity. This study aimed to evaluate the public perception of vaccination certificates as a primary outcome while assessing differences between sociodemographic groups as secondary outcome measures.

Methods

Study setting and data collection

In the spring of 2021, a self-administered online questionnaire was proposed to all persons 18 years and older participating in the longitudinal follow-up of SARS-CoV-2 seroprevalence studies in Geneva, Switzerland [17, 18]. This longitudinal follow-up is conducted via the Specchio-COVID19 platform, which allows participants to answer regular online questionnaires [19]. The Specchio-COVID19 platform launched in December 2020 follows up individuals who have participated in seroprevalence studies in the canton of Geneva. Participants were randomly selected from the general population at two time-points, first between April and June 2020, with individuals participating in a previous general health study (Bus Santé, an annual health examination survey of a sample representative of the Geneva population [17, 20]); and second between November and December 2020 with individuals  randomly selected from population registries of the canton of Geneva [18].

All individuals gave consent, and the study was approved by the Cantonal Research Ethics Commission of Geneva, Switzerland (protocol numbers CER 2020–01540 and CER 2020–00881). Questions about vaccination certificates were part of a larger vaccination questionnaire (analysis submitted to Swiss Medical Weekly). Specific questions about vaccination certificates were elaborated based on the results of the initial questionnaire on the perception of immunity certificates [16], as well as the results of a qualitative study conducted between July and November 2020, aimed at identifying arguments for or against immunity certificates [21]. An initial invitation to complete the questionnaire was sent by e-mail on 17 March 17 with a reminder 2 weeks later. We included participants who answered between 17 March and 1 April 2021.

The questionnaire (table S1 in the appendix) was collaboratively constructed by physicians (IG, MN), epidemiologists (IG, SS, HB), sociologists (CBJ, VF), and an ethicist (SH). Two main questions were asked: (1) Select the context(s) in which a vaccination certificate should be presented (with a list of contexts); (2) What is your opinion about the following statements on the implementation of a COVID-19 vaccination certificate (with a list of statements)? The answers to the latter question were based on a five-point Likert scale with the following categories: 1 “strongly disagree”; 2 “disagree”; 3 “neither agree nor disagree”; 4 ”agree”; 5 ”strongly agree” (table S1 in the appendix for details).

Education was categorised as follows: “primary” included compulsory education and no formal education; “apprenticeship” included apprenticeships; “secondary” included secondary school and specialised schools; “tertiary” included universities, higher professional education and doctorates. Occupational position was categorised as follows: unskilled workers were qualified employees practising manual labour, craftsmen, traders, farmers and employees without specific training; skilled workers were qualified employees (non-manual labour); highly skilled workers were employees with a profession requiring intermediate training; professional-managers were company managers with more than 10 employees or individuals with a profession requiring university training; independent workers were individuals who worked as consultants, were independent or were company managers with fewer than 10 employees. Household income was calculated taking into consideration household revenue and the number of individuals in a household. Household income was then compared with the cantonal database available online [22] with the categories defined as “low” (below first quartile); “mid” (between quartiles 1 and 3); “High” (higher than the third quartile). Individuals were considered to have a prior SARS-CoV-2 infection if self-reported or if their serological test was positive for anti-SARS-CoV-2 antibodies as part of the seroprevalence studies. COVID-19 vaccination willingness was defined as the combined answer to the following two questions used in the larger vaccination questionnaire: “Did you get vaccinated against SARS-CoV-2? (yes, no, scheduled appointment)” and “Do you intend to get vaccinated once you will be eligible for vaccination against SARS-CoV-2? (yes, rather yes, rather no, no, does not know, not available)”. Answers “yes” and “scheduled appointment” to the first question and answers “yes” and “rather yes” to the second question were later combined as willingness to get vaccinated. Answer “no” to the first question, and answers "no” and “rather no” to the second question were later combined as not willing to get vaccinated. Vaccination perception was defined as the answer to the question used in the larger vaccination questionnaire: “Do you think that vaccination is an important step to surmount the pandemic?” (yes, rather yes, rather no, no).

Analysis

We used the statistical software STATA version 15.1. Descriptive analyses included percentages with comparisons using chi-square tests. P-values were considered significant at p <0.05. Stratifications were based on age categories, sex, education level, household income, employment status, occupational position, past SARS-CoV-2 infection, vaccination willingness and vaccination perception.

Logistic regression models were used to evaluate associations between different determinants and the absence of any context in which participants believed a vaccination certificate should be presented. The determinants considered were age, sex, education level, household income, employment status, occupational position, past SARS-CoV-2 infection, vaccination willingness and vaccination perception. The outcome was certificate non-acceptance, defined by the variable “There is no context in which a vaccination certificate should be presented”. Multivariable regression models were then used to calculate adjusted odds ratios (aORs) with a 95% confidence interval (95% CI). Adjusted odds ratios were adjusted for age, sex, education level, household income, employment status, occupational position, past SARS-CoV-2 infection, vaccination willingness and vaccination perception. Missing values were handled using listwise deletion with a complete-case analysis approach. The intersex category as well as the “not available” (NA) categories for all variables were excluded from the logistical regression analysis due to low counts. Participants answering “I do not know or prefer not to answer” were included when adjusting for variables in the regression analysis, but estimates were not calculated for these categories in order to avoid misclassification.

Results

Out of 5252 individuals, 4067 answered the questionnaire (response rate 77.4%). Mean age (± standard deviation) was 53.3 ± 14.4 years, 56.1% were women, 64.7% had completed tertiary education, 64.8% had a middle to high income, 25.9% were retirees and 4% were students. Non-participants (n = 1185) had a mean age (± standard deviation) of 43.7 ± 14.4 years, 53.3% were women, 63.2% had completed tertiary education, 55.9% had middle to high income, 9.8% were retirees and 12% were students. Overall characteristics of participants are presented in table 1 and a comparison with the general population of Geneva [23] is available in table S2 in the appendix.

Overall, 61.0% of participants agreed or strongly agreed that a vaccination certificate is necessary in certain contexts and 21.6% believed there was no context where vaccination certificates should be presented, defined as certificate non-acceptance (table 2). Not willing to get vaccinated (aOR 8.29, 95% CI 6.45–10.68) and not perceiving vaccination as an important step to surmount the pandemic (aOR 4.17, 95% CI 2.86–6.08) were associated with certificate non-acceptance. Past SARS-CoV-2 infection (OR 1.53, 95% CI 1.27–1.82), age 65 years and older (OR 0.29, 95% CI 0.22–0.40), and female gender (OR 1.40, 95% CI 1.20–1.63) were associated with certificate non-acceptance in the univariate analyses but not when adjusted in the multivariable analyses. High household income (OR 0.68, 95% CI 0.50–0.91) and being a professional manager (OR 0.67, 95% CI 0.51–0.89) were inversely associated with certificate non-acceptance in the univariate analyses but not when adjusted in the multivariable analyses (table 3).

When selecting contexts, 60.7% of participants found that a vaccination certificate should be presented in order to hold a job or position that requires contact with populations at risk of complications from COVID-19 (working in a nursing home, for example) and 47.6% of participants believed a vaccination certificate should be presented when visiting individuals at risk of complications from COVID-19. Overall, 58.7% of participants found that a vaccination certificate should be presented in order to hold a job or position that required contact with infected individuals (working at a hospital for example) and 21.5% considered that a vaccination certificate should be presented if employees were sharing the same open workspace.

When considering collective versus individual benefit, 32.2% believed a vaccination certificate should be presented in order to cross international borders, 44.3% of participants believed such certificates should be presented to take a plane and 56.0% of participants believed they should be presented in order to avoid quarantine when crossing international borders. With regard to specific activities, 36.9% of participants believed vaccination certificates should be presented in order to participate in large gatherings and 35.5% in order to have access to social venues (cinema, theatre, gym, etc.).

Overall, 62.1% agreed or strongly agreed that it was easier to accept vaccination certificates than the public health restrictions in place at the time of the questionnaire, and 12.5% agreed or strongly agreed with the statement that COVID-19 was a trivial disease that did not require a vaccination certificate. When discussing potential risks, 40.0% of participants agreed or strongly agreed that vaccination status constituted personal medical data that should not be the subject of a vaccination certificate, 58.4% of participants agreed or strongly agreed that individuals without a vaccination certificate could be at risk of discrimination (employment opportunities or participating in certain activities, for example) and 66.5% agreed or strongly agreed that individuals without a vaccination certificate could lose certain rights (crossing borders, for example).

Stratification by age, sex, education level, household income, employment status, occupational position, past SARS-CoV-2 infection, vaccination willingness and vaccination perception is presented in appendix table S3.

Vaccination willingness and perception

Overall, 66.0% of individuals who did not or will not get vaccinated (371 out of 562) did not believe there was any context where a vaccination certificate should be presented versus 10.9% of individuals who reported they had been or intended to get vaccinated (336 out of 3080). Additionally, participants who did not believe vaccination to be an important step in surmounting the COVID-19 pandemic rejected all contexts of vaccination certificates, with 76.8% of them seeing no context where vaccination certificates should be presented (241 out of 314) versus 17.0% of individuals who believed vaccination to be an important step in surmounting the COVID-19 pandemic (637 out of 3753). Participants who did not believe vaccination to be an important step in surmounting the COVID-19 pandemic were also more likely to perceive a discrimination risk against individuals without a vaccination certificate, were more likely to agree that vaccination status was personal data that should not be the subject of a vaccination certificate, and were less likely to agree that certificates were easier to accept than the public health restrictions in place at the time of the questionnaire.

Past SARS-CoV-2 infection

Participants who had been infected with SARS-CoV-2 were less likely to support vaccination certificates. Overall, 27.8% of individuals who had been infected did not believe there was any context where a vaccination certificate should be presented versus 20.1% of individuals who had not been infected. Additionally, 47.2% of previously infected individuals were likely to agree or strongly agree that vaccination status was personal medical data that should not be the subject of a vaccination certificate versus 38.2% of individuals who had not been infected. Of previously infected individuals, 15.2% agreed or strongly agreed with the statement that COVID-19 was a trivial disease not necessitating a vaccination certificate versus 11.8% of non-infected individuals.

Sociodemographic characteristics

Older individuals were more likely to agree with a vaccination certificate overall, whether in a professional, travel or social context. They were more likely to disagree with the statement that COVID-19 was a trivial disease not necessitating a vaccination certificate. Younger individuals were more likely to agree or strongly agree that individuals without vaccination certificates might lose certain rights or be at risk of discrimination.

Men were more inclined to agree with the use of vaccination certificates in all listed contexts, and when compared with the public health measures in place at the time of the questionnaire, they were also less likely to agree that individuals without vaccination certificates might face discrimination or lose certain rights. Women more strongly agreed that vaccination status constituted personal medical data that should not be the subject of a vaccination certificate.

Individuals with a tertiary education were more likely to agree with the statement that vaccination certificates were needed in professional settings where others would be at risk of COVID-related complications or where the employee might be at risk of infection, whereas no difference was seen in contexts of travel, access to social venues or large gatherings. Individuals with a tertiary education were less likely to agree with the statement that vaccination status constituted personal medical data that should not be the subject of a certificate.

Individuals with a low household income agreed less overall with the use of vaccination certificates. They were more likely to agree that COVID-19 was a trivial disease not necessitating a vaccination certificate and that vaccination status constituted personal medical data that should not be the subject of a certificate. They were less likely to agree that individuals without a vaccination certificate were at risk of discrimination or may lose certain rights. They were also less likely to agree that it would be easier to accept vaccination certificates than the public health restrictions in place at the time of the questionnaire.

Managers were more inclined to agree with vaccination certificates in all contexts. More participants in the professional managers category agreed that vaccination certificates should be presented to take a plane or to be exempt from quarantine when travelling abroad. Fewer participants in the professional-managers category agreed that vaccination status constituted personal medical data that should not be the subject of a certificate.

Discussion

Using a large population-based study, we found that 61.0% of individuals agreed or strongly agreed that a vaccination certificate is necessary in certain contexts, and 62.1% agreed or strongly agreed that it was easier to accept vaccination certificates than the public health restrictions in place at the time of the questionnaire. Certificate non-acceptance (overall 21.6%) was more prevalent in younger age categories and was associated with an absence of willingness to get vaccinated and an absence of belief in vaccination as an important step in surmounting the pandemic. Overall, 27.8% of 18–34 years old reported certificate non-acceptance versus 10.2% of individuals 65 years and older. By comparison, a recent French survey (n = 3058) reported a 34.1% overall certificate non-acceptance rate (44.4% in individuals 18–34 years old versus 16.7% in individuals 65 years and older) [24], and a UK-based public poll (n = 1715) reported a 34% overall certificate non-acceptance rate (42% in individuals 18–24 and 25–49 years old versus 20% in individuals 65 years and older) [25]. In the UK, a recent study estimated a 78.71% vaccination intent rate in the population, but that the introduction of vaccine passports would lower vaccination acceptance further in the subgroups not willing to get vaccinated. The lower inclination to get vaccinated was more evident in males and individuals who were more highly educated after adjusting for baseline vaccination intent [13]. There was also a strong association between vaccination intent and the acceptance of vaccination certificates, as seen in our study. The latest reports of vaccination in the general population in Geneva showed higher vaccination rates with age as of 14 September 2021 [26]. As participants in our sample were older overall, we could predict that certificate acceptance would be lower in the general population. When  data in our sample were standardised to the age, sex and education distribution of the Geneva population, we estimate certificate acceptance at 57.7% and certificate non-acceptance at 22.4%.

Contexts where a majority of participants perceived a vaccination certificate should be presented included jobs where others would be at risk of COVID-related complications and jobs where employees were at risk of getting infected. This is in line with recent articles showing the need for safeguards around work-related vaccination policies that should be based on the actual risk to workers’ or customers’ health [2, 27]. The majority of participants were also in favour of a vaccination certificate when presented with the option of quarantine exemption if traveling abroad, which could be a way to reinvigorate the tourism and travel sectors that have suffered greatly during the pandemic. On the other hand, participants were less in favour of a vaccination certificate in order to participate in large gatherings or to access social venues, where it might be up to private actors to decide whether vaccines are mandatory, thus potentially influencing vaccination uptake [2]. Interestingly, in a canton that borders France and where many individuals cross borders frequently, only 32.2% believed vaccination certificates should be presented to cross borders, whereas 44.3% believed they should be presented to take a plane. This could also be due to the perception or impression of an increased risk of infection when taking a plane versus other means of transportation. A public poll in the UK in March 2021 [25] revealed that 72% of participants believed vaccination certificates should be required to visit nursing homes, followed by gyms (56%), pubs and bars (56%), cinemas (55%), restaurants (53%), public transport (45%) and supermarkets (31%) underlining the differences in acceptability according to context [25].

The majority of individuals perceived risks of discrimination and loss of certain rights for those without a vaccination certificate. Forty percent perceived vaccination status as personal medical data that should not be part of a vaccination certificate. Although vaccination certificates risk infringing on civil liberties by putting pressure on individuals to share their information, it must be recognised that lockdown measures and the pandemic itself have also represented a burden on civil liberties such as free movement or allowing people to return to work [1]. This was evidenced in our study, where a majority of participants agreed that it was easier to accept a vaccination certificate than the public health restrictions in place at the time of the questionnaire.

Women were less likely to agree with the latter statement, as well as less likely to agree with vaccination certificates in all the listed contexts, indicating they were overall less in favour of vaccination certificates. Similar results were reported in a recent publication showing that female scholars were significantly less in favour of immunity certificates [15]. Gender differences were less evident in the multivariable analyses in our study. Individuals who had been infected were less inclined to agree with vaccination certificates. This could be because a higher percentage of previously infected individuals agreed with the statement that COVID-19 was a trivial disease not necessitating a vaccination certificate, or because of their lower perceived personal need for vaccination, having themselves acquired natural immunity.

When these results were compared with those of our previous survey in May–June 2020 [16], individuals still believed immunity certificates were important in certain contexts but not all, while identifying potential risks of discrimination or losing certain rights. It is important to note that the risk of deliberate infection as a means to obtain a certificate should decrease with the advent of vaccination, as individuals could now make the decision to get vaccinated. That being said, it is also important to take into account that universal access to vaccines remained an issue at the time of our study, especially in low and middle income countries.

Our study adds to the general body of knowledge by providing information on the importance of taking into account differences in the perception of vaccination and the disease itself when implementing vaccination certificates. Although disagreements exist regarding the justification and appropriate use of vaccination certificates on ethical grounds [28, 29], the likely public uptake of such certificates is an important factor in considering their implementation. Vaccination certificates should not be a blanket solution, however, and ought to be tailored to specific contexts instead.

This study has several limitations. First, the questionnaire was not pre-tested and was only available online and in French. Participants were all recruited from the seroprevalence studies, were generally older, with a higher education level and a higher socioeconomic status than the overall population of Geneva, limiting the generalisability of the results. Second, the timing of the questionnaire when partial lockdown measures were still in effect in Switzerland and when vaccination was only available to individuals 65 years and older or individuals with chronic diseases at risk of COVID-related complications, could have influenced opinions which could change over time. The survey will be repeated over time, addressing this limitation. Third, our study evaluated vaccination certificates only, rather than the three-modality certificates deployed in Switzerland and the EU. Fourth, participants were potentially unlikely to be aware of the advantages or disadvantages of the studied intervention, as is usually the case in survey research.

Conclusion

Vaccination certificates appear to be supported by the majority of the general population in Geneva, Switzerland, especially in contexts of quarantine exemption and where work-related transmission of SARS-CoV-2 would be reduced for individuals at risk of complications or infection. Vaccination certificates are less accepted in contexts of large gatherings, access to social venues or shared workspaces. When implemented, it is important to address and communicate the role of vaccination certificates as a transition strategy in facilitating a collective phased return to pre-COVID activities by providing reassurance to individuals pursuing these activities as to their reduced risk of transmitting or acquiring an infection. Vaccination certificates should be met with a targeted implementation, adapting them to certain contexts, and modifying or cancelling them when they are no longer needed. Implementation strategies should take into consideration personal and sociodemographic variations in certificate non-acceptance, highlighting the importance of tailoring communication to younger individuals, those who may not agree with vaccination against SARS-CoV-2, and those who believe COVID-19 to be a trivial disease.

Data sharing statement

Individual study data that underlie the results reported in this article can be made available to the scientific community after de-identification and upon submission of a data request application to the investigator board via the corresponding author.

Specchio-COVID19 study group

Isabelle Arm-Vernez, Andrew S Azman, Fatim Ba, Oumar Aly Ba, Delphine Bachmann, Jean-François Balavoine, Michael Balavoine, Hélène Baysson, Lison Beigbeder, Julie Berthelot, Patrick Bleich, Gaëlle Bryand, François Chappuis, Prune Collombet, Delphine S. Courvoisier, Alain Cudet, Carlos de Mestral Vargas, Paola D'Ippolito, Richard Dubos, Roxane Dumont, Isabella Eckerle, Nacira El Merjani, Antoine Flahault, Natalie Francioli, Marion Frangville, Idris Guessous, Séverine Harnal, Samia Hurst, Laurent Kaiser, Omar Kherad, Julien Lamour, Pierre Lescuyer, François LHuissier, Fanny-Blanche Lombard, Andrea Jutta Loizeau, Elsa Lorthe, Chantal Martinez, Lucie Ménard, Lakshmi Menon, Ludovic Metral-Boffod, Alexandre Moulin, Mayssam Nehme, Natacha Noël, Francesco Pennacchio, Javier Perez-Saez, Giovanni Piumatti, Didier Pittet, Jane Portier, Klara M Posfay-Barbe, Géraldine Poulain, Caroline Pugin, Nick Pullen, Zo Francia Randrianandrasana, Aude Richard, Viviane Richard, Frederic Rinaldi, Jessica Rizzo, Khadija Samir, Claire Semaani, Silvia Stringhini, Stéphanie Testini, Guillemette Violot, Nicolas Vuilleumier, Ania Wisniak, María-Eugenia Zaballa

Appendix

The appendix is available in the PDF version of this article.

References

1. Brown RC , Savulescu J , Williams B , Wilkinson D . Passport to freedom? Immunity passports for COVID-19. J Med Ethics. 2020 Oct;46(10):652–9. https://doi.org/10.1136/medethics-2020-106365  

2. Hall MA , Studdert DM . “Vaccine Passport” Certification - Policy and Ethical Considerations. N Engl J Med. 2021 Sep;385(11):e32. https://doi.org/10.1056/NEJMp2104289; Epub ahead of print.  

3. Saladino V , Algeri D , Auriemma V . The Psychological and Social Impact of Covid-19: New Perspectives of Well-Being. Front Psychol. 2020 Oct;11:577684. https://doi.org/10.3389/fpsyg.2020.577684  

4. Childress JF , Faden RR , Gaare RD , Gostin LO , Kahn J , Bonnie RJ , et al.  Public health ethics: mapping the terrain. J Law Med Ethics. 2002;30(2):170–8. https://doi.org/10.1111/j.1748-720X.2002.tb00384.x  

5. Osama T , Razai MS , Majeed A . Covid-19 vaccine passports: access, equity, and ethics. BMJ. 2021 Apr;373(861):n861. https://doi.org/10.1136/bmj.n861  

6. European Commission . EU Digital COVID Certificate https://ec.europa.eu/health/ehealth/covid-19_en. Published April 21, 2021. [Accessed 23 September 2021] 

7. Federal Office of Public Health . Switzerland. Coronavirus: COVID certificate. https://www.bag.admin.ch/bag/en/home/krankheiten/ausbrueche-epidemien-pandemien/aktuelle-ausbrueche-epidemien/novel-cov/covid-zertifikat.html. [Accessed 23 September 2021] 

8. Brown RC , Kelly D , Wilkinson D , Savulescu J . The scientific and ethical feasibility of immunity passports. Lancet Infect Dis. 2021 Mar;21(3):e58–63. https://doi.org/10.1016/S1473-3099(20)30766-0  

9. Schmelz K . Enforcement may crowd out voluntary support for COVID-19 policies, especially where trust in government is weak and in a liberal society. Proc Natl Acad Sci USA. 2021 Jan;118(1):e2016385118. https://doi.org/10.1073/pnas.2016385118  

10. Sesa G , Wong B , Czabanowska K , Reid J , Davidovitch N , Martin-Moreno JM , Middleton J . Covid-19 vaccine passports and vaccine hesitancy: freedom or control? BMJ opinion. March 30, 2021. 

11. Wilf-Miron R , Myers V , Saban M . Incentivizing Vaccination Uptake: The “Green Pass” Proposal in Israel. JAMA. 2021 Apr;325(15):1503–4. https://doi.org/10.1001/jama.2021.4300  

12. Lazarus JV , Ratzan SC , Palayew A , Gostin LO , Larson HJ , Rabin K , et al.  A global survey of potential acceptance of a COVID-19 vaccine [Erratum in: Nat Med. 2021 Jan 11; PMID: 33082575; PMCID: PMC7573523]. Nat Med. 2021 Feb;27(2):225–8. https://doi.org/10.1038/s41591-020-1124-9  

13. de Figueiredo A , Larson HJ , Reicher S . The potential impact of vaccine passports on inclination to accept COVID-19 vaccinations in the United Kingdom: evidence from a large cross-sectional survey and modelling study. medRxiv 2021;2021.05.31.21258122. 

14. Drury J , Mao G , John A , et al.  Behavioural responses to Covid-19 health certification: A rapid review. medRxiv 2021;2021.04.07.21255072. 

15. Aranzales I , Chan HF , Eichenberge R , Hegselmann R , Stadelmann D , Torgler B . Scientists’ Opinions on Immunity Certificates: Evidence from a Large-Scale Survey Among more than 12,000 Scientists (No. 2021-08). Center for Research in Economics, Management and the Arts (CREMA). 

16. Nehme M , Stringhini S , Guessous I ; SEROCoV-Pop Study Team . Perceptions of immunity and vaccination certificates among the general population: a nested study within a serosurvey of anti-SARS-CoV-2 antibodies (SEROCoV-POP). Swiss Med Wkly. 2020 Nov;150:w20398. https://doi.org/10.4414/smw.2020.20398  

17. Stringhini S , Wisniak A , Piumatti G , Azman AS , Lauer SA , Baysson H , et al.  Seroprevalence of anti-SARS-CoV-2 IgG antibodies in Geneva, Switzerland (SEROCoV-POP): a population-based study. Lancet. 2020 Aug;396(10247):313–9. https://doi.org/10.1016/S0140-6736(20)31304-0  

18. Stringhini S , Zaballa ME , Perez-Saez J , Pullen N , de Mestral C , Picazio A , et al.; Specchio-COVID19 Study Group . Seroprevalence of anti-SARS-CoV-2 antibodies after the second pandemic peak. Lancet Infect Dis. 2021 May;21(5):600–1. https://doi.org/10.1016/S1473-3099(21)00054-2  

19. Baysson H , Pennacchio F , Wisniak A , Zaballa ME , Collombet P , Joost S , Balavoine JF , Bachmann D , Trono D , Pittet D , Chappuis F , Kherad O , Kaiser L , Guessous I , Stringhini S , on behalf of the Specchio COVID19 study group The Specchio-COVID19 study cohort: a web-based prospective study of SARS-CoV-2 serosurveys participants in the canton of Geneva (Switzerland) (in preparation). 

20. de Mestral C , Stringhini S , Guessous I , Jornayvaz FR . Thirteen-year trends in the prevalence of diabetes in an urban region of Switzerland: a population-based study. Diabet Med. 2020 Aug;37(8):1374–8. https://doi.org/10.1111/dme.14206  

21. Fargnoli V , Nehme M , Guessous I , Burton-Jeangros C . Acceptability of COVID-19 Certificates: A Qualitative Study in Geneva, Switzerland, in 2020. Front Public Health. 2021 Aug;9:682365. https://doi.org/10.3389/fpubh.2021.682365  

22. Office Cantonal des Statistiques (OCSTAT) . T 20.02.7.01 - Statistique cantonale du revenu et de la fortune des ménages - Quantiles du revenu annuel brut des ménages selon le type de ménage en 2015-2017 - Canton de Genève. 2020. [Accessed 23 September 2021] 

23. Office cantonal des statistiques (OCSTAT) STATISTIQUES CANTONALES, POPULATION, Etat et évolution de la population. Version 2020. Available at: https://www.ge.ch/statistique/domaines/apercu.asp?dom=01_01 [Accessed 12 September 2021]. 

24. Ward J , Bonneton M , Botelho-Nevers E , et al. Enquête COVIREIVAC: les français et la vaccination. ORS PACA- June 2021. 

25. YouGov . Would Britons support a vaccine passport for COVID-19? [Internet]. YouGov; 2021 March 5. Available from: https://yougov.co.uk/topics/health/articles-reports/2021/03/05/britons-support-covid-19-vaccine-passport-system. [Accessed 23 September 2021] 

26. Direction générale de la santé Chiffres et campagne de vaccination à Genève Available at https://www.ge.ch/se-faire-vacciner-contre-covid-19/chiffres-campagne-vaccination-geneve [Accessed September 15 2021]. 

27. Hall MA , Studdert D . Public Views about COVID-19 “Immunity Passports” medRxiv 2021.01.26.21250184; doi: https://doi.org/https://doi.org/10.1101/2021.01.26.21250184  

28. Voo TC , Reis AA , Thomé B , Ho CW , Tam CC , Kelly-Cirino C , et al.  Immunity certification for COVID-19: ethical considerations. Bull World Health Organ. 2021 Feb;99(2):155–61. https://doi.org/10.2471/BLT.20.280701  

29. Kofler N , Baylis F. Covid-19 vaccination certificates: Prospects and problems. The Hastings Center. March 10, 2021.