Research Open Access
Like 0



Up-to-date seroprevalence estimates are critical to describe the SARS-CoV-2 immune landscape and to guide public health decisions.


We estimate seroprevalence of anti-SARS-CoV-2 antibodies 15 months into the COVID-19 pandemic and 6 months into the vaccination campaign.


We conducted a population-based cross-sectional serosurvey between 1 June and 7 July 2021, recruiting participants from age- and sex-stratified random samples of the general population. We tested participants for anti-SARS-CoV-2 antibodies targeting the spike (S) or nucleocapsid (N) proteins using the Roche Elecsys immunoassays. We estimated the anti-SARS-CoV-2 antibodies seroprevalence following vaccination and/or infection (anti-S antibodies), or infection only (anti-N antibodies).


Among 3,355 individuals (54.1% women; 20.8% aged < 18 years and 13.4% aged ≥ 65 years), 2,161 (64.4%) had anti-S antibodies and 906 (27.0%) had anti-N antibodies. The total seroprevalence was 66.1% (95% credible interval (CrI): 64.1–68.0). We estimated that 29.9% (95% Crl: 28.0–31.9) of the population developed antibodies after infection; the rest having developed antibodies via vaccination. Seroprevalence estimates differed markedly across age groups, being lowest among children aged 0–5 years (20.8%; 95% Crl: 15.5–26.7) and highest among older adults aged ≥ 75 years (93.1%; 95% Crl: 89.6–96.0). Seroprevalence of antibodies developed via infection and/or vaccination was higher among participants with higher educational level.


Most of the population has developed anti-SARS-CoV-2 antibodies, despite most teenagers and children remaining vulnerable to infection. As the SARS-CoV-2 Delta variant spreads and vaccination rates stagnate, efforts are needed to address vaccine hesitancy, particularly among younger individuals and to minimise spread among children.


Article metrics loading...

Loading full text...

Full text loading...



  1. Campbell F, Archer B, Laurenson-Schafer H, Jinnai Y, Konings F, Batra N, et al. Increased transmissibility and global spread of SARS-CoV-2 variants of concern as at June 2021. Euro Surveill. 2021;26(24):2100509.  https://doi.org/10.2807/1560-7917.ES.2021.26.24.2100509  PMID: 34142653 
  2. European Centre for Disease Prevention and Control (ECDC). COVID-19 vaccine rollout report week 33. Stockholm: ECDC; 2021. Available from: https://covid19-vaccine-report.ecdc.europa.eu/
  3. Murhekar MV, Clapham H. COVID-19 serosurveys for public health decision making. Lancet Glob Health. 2021;9(5):e559-60.  https://doi.org/10.1016/S2214-109X(21)00057-7  PMID: 33705691 
  4. République et Canton de Genève (Republic and Canton of Geneva). COVID-19 à Genève. Données cantonales [COVID-19 in Geneva. Cantonal data]. Geneva: Republic and Canton of Geneva. [Accessed: 11 Aug 2021]. French. Available from: https://infocovid.smc.unige.ch
  5. Stringhini S, Zaballa M-E, Perez-Saez J, Pullen N, de Mestral C, Picazio A, et al. Seroprevalence of anti-SARS-CoV-2 antibodies after the second pandemic peak. Lancet Infect Dis. 2021;21(5):600-1.  https://doi.org/10.1016/S1473-3099(21)00054-2  PMID: 33539733 
  6. Canto e Castro L, Gomes A, Serrano M, Pereira AH, Ribeiro R, Napoleão P, et al. Longitudinal SARS-CoV-2 seroprevalence in Portugal and antibody maintenance 12 months after the start of the COVID-19 pandemic. Research Square.2021; Preprint.  https://doi.org/10.21203/rs.3.rs-603060/v1 
  7. 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;396(10247):313-9.  https://doi.org/10.1016/S0140-6736(20)31304-0  PMID: 32534626 
  8. Perez-Saez J, Zaballa M-E, Yerly S, Andrey DO, Meyer B, Eckerle I, et al. Persistence of anti-SARS-CoV-2 antibodies: immunoassay heterogeneity and implications for serosurveillance. Clin Microbiol Infect. 2021;S1198-743X(21)00371-2.  https://doi.org/10.1016/j.cmi.2021.06.040  PMID: 34245905 
  9. L’Huillier AG, Meyer B, Andrey DO, Arm-Vernez I, Baggio S, Didierlaurent A, et al. Antibody persistence in the first 6 months following SARS-CoV-2 infection among hospital workers: a prospective longitudinal study. Clin Microbiol Infect. 2021;27(5):784.e1-8.  https://doi.org/10.1016/j.cmi.2021.01.005  PMID: 33482352 
  10. Wheeler SE, Shurin GV, Yost M, Anderson A, Pinto L, Wells A, et al. Differential antibody response to mRNA COVID-19 vaccines in healthy subjects. Microbiol Spectr. 2021;9(1):e0034121.  https://doi.org/10.1128/Spectrum.00341-21  PMID: 34346750 
  11. Stan Development Team. Rstan: the R interface to Stan. R package version 2.21.2. 2020. Available from: https://mc-stan.org
  12. European Centre for Disease Prevention and Control (ECDC). SARS-CoV-2-increased circulation of variants of concern and vaccine rollout in the EU/EEA, 14th update. Stockholm: ECDC; 2021. Available from: https://www.ecdc.europa.eu/sites/default/files/documents/RRA-15th-update-June%202021.pdf
  13. Bajema KL, Wiegand RE, Cuffe K, Patel SV, Iachan R, Lim T, et al. Estimated SARS-CoV-2 seroprevalence in the US as of September 2020. JAMA Intern Med. 2021;181(4):450-60.  https://doi.org/10.1001/jamainternmed.2020.7976  PMID: 33231628 
  14. République et Canton de Genève (Republic and Canton of Geneva). Vaccination in Geneva: numbers and campaign in Geneva. Geneva: Republic and Canton of Geneva. [Accessed: 15 Jul 2021]. Available from: https://www.ge.ch/en/node/23804
  15. Bartleson JM, Radenkovic D, Covarrubias AJ, Furman D, Winer DA, Verdin E. SARS-CoV-2, COVID-19 and the aging immune system. Nat Aging.2021;1(9):769-82.  https://doi.org/10.1038/s43587-021-00114-7 
  16. Collier DA, Ferreira IATM, Kotagiri P, Datir RP, Lim EY, Touizer E, et al. Age-related immune response heterogeneity to SARS-CoV-2 vaccine BNT162b2. Nature. 2021;596(7872):417-22.  https://doi.org/10.1038/s41586-021-03739-1  PMID: 34192737 
  17. Barry V, Dasgupta S, Weller DL, Kriss JL, Cadwell BL, Rose C, et al. Patterns in COVID-19 vaccination coverage, by social vulnerability and urbanicity - United States, December 14, 2020-May 1, 2021. MMWR Morb Mortal Wkly Rep. 2021;70(22):818-24.  https://doi.org/10.15585/mmwr.mm7022e1  PMID: 34081685 
  18. Caspi G, Dayan A, Eshal Y, Liverant-Taub S, Twig G, Shalit U, et al. Socioeconomic disparities and COVID-19 vaccination acceptance: a nationwide ecologic study. Clin Microbiol Infect. 2021;27(10):1502-6.  https://doi.org/10.1016/j.cmi.2021.05.030  PMID: 34111591 
  19. Richard A, Wisniak A, Perez-Saez J, Garrison-Desany H, Petrovic D, Piumatti G, et al. Seroprevalence of anti-SARS-CoV-2 IgG antibodies, risk factors for infection and associated symptoms in Geneva, Switzerland: a population-based study. Scand J Public Health. 2021;14034948211048050. PMID: 34664529 
  20. Niedzwiedz CL, O’Donnell CA, Jani BD, Demou E, Ho FK, Celis-Morales C, et al. Ethnic and socioeconomic differences in SARS-CoV-2 infection: prospective cohort study using UK Biobank. BMC Med. 2020;18(1):160.  https://doi.org/10.1186/s12916-020-01640-8  PMID: 32466757 
  21. Wachtler B, Michalski N, Nowossadeck E, Diercke M, Wahrendorf M, Santos-Hövener C, et al. Socioeconomic inequalities in the risk of SARS-CoV-2 infection – First results from an analysis of surveillance data from Germany. J Health Monit.2020;S7:18-29.  https://doi.org/10.25646/7057 
  22. Clouston SAP, Natale G, Link BG. Socioeconomic inequalities in the spread of coronavirus-19 in the United States: A examination of the emergence of social inequalities. Soc Sci Med. 2021;268:113554.  https://doi.org/10.1016/j.socscimed.2020.113554  PMID: 33308911 
  23. Wisniak A, Baysson H, Pullen N, Nehme M, Pennacchio F, Zaballa M-E, et al. COVID-19 vaccination acceptance in the canton of Geneva: a cross-sectional population-based study. medRxiv. 2021;2021.07.05.21260024. Preprint.
  24. Paul E, Steptoe A, Fancourt D. Attitudes towards vaccines and intention to vaccinate against COVID-19: Implications for public health communications. Lancet Reg Health Eur. 2021;1:100012.  https://doi.org/10.1016/j.lanepe.2020.100012  PMID: 33954296 
  25. Sonawane K, Troisi CL, Deshmukh AA. COVID-19 vaccination in the UK: Addressing vaccine hesitancy. Lancet Reg Health Eur. 2021;1:100016.  https://doi.org/10.1016/j.lanepe.2020.100016  PMID: 34173622 
  26. Viswanath K, Bekalu M, Dhawan D, Pinnamaneni R, Lang J, McLoud R. Individual and social determinants of COVID-19 vaccine uptake. BMC Public Health. 2021;21(1):818.  https://doi.org/10.1186/s12889-021-10862-1  PMID: 33910558 
  27. Rhodes A, Hoq M, Measey M-A, Danchin M. Intention to vaccinate against COVID-19 in Australia. Lancet Infect Dis. 2021;21(5):e110.  https://doi.org/10.1016/S1473-3099(20)30724-6  PMID: 32941786 
  28. Peretti-Watel P, Seror V, Cortaredona S, Launay O, Raude J, Verger P, et al. A future vaccination campaign against COVID-19 at risk of vaccine hesitancy and politicisation. Lancet Infect Dis. 2020;20(7):769-70.  https://doi.org/10.1016/S1473-3099(20)30426-6  PMID: 32445713 
  29. Accorsi EK, Qiu X, Rumpler E, Kennedy-Shaffer L, Kahn R, Joshi K, et al. How to detect and reduce potential sources of biases in studies of SARS-CoV-2 and COVID-19. Eur J Epidemiol. 2021;36(2):179-96.  https://doi.org/10.1007/s10654-021-00727-7  PMID: 33634345 
  30. Chia WN, Zhu F, Ong SWX, Young BE, Fong S-W, Le Bert N, et al. Dynamics of SARS-CoV-2 neutralising antibody responses and duration of immunity: a longitudinal study. Lancet Microbe. 2021;2(6):e240-9.  PMID: 33778792 

Data & Media loading...

Supplementary data

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error