Seroprevalence of anti-SARS-CoV-2 antibodies six months into the vaccination campaign in Geneva, Switzerland

Abstract

Background: Up-to-date seroprevalence estimates are critical to describe the SARS-CoV-2 immune landscape in the population and guide public health measures. We aimed to estimate the seroprevalence of anti-SARS-CoV-2 antibodies 15 months into the COVID-19 pandemic and six months into the vaccination campaign. Methods: We conducted a population-based cross-sectional serosurvey between June 1 and July 7, 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 (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). Results: We included 3355 individuals, of which 1814 (54.1%) were women, 697 (20.8%) were aged <18 years and 449 (13.4%) were aged ≥65 years, 2161 (64.4%) tested positive for anti-S antibodies, and 906 (27.0%) tested positive for anti-N antibodies. The total seroprevalence of anti-SARS-CoV-2 antibodies was 66.1% (95% credible interval, 64.1-68.0). Considering the presence of anti-N antibodies, we estimated that 29.9% (28.0-31.9) of the population developed antibodies after infection; the rest having developed antibodies only via vaccination. Seroprevalence estimates were similar across sexes, but differed markedly across age groups, being lowest among children aged 0-5 years (20.8% [15.5-26.7]) and highest among older adults aged ≥75 years (93.1% [89.6-96.0]). Seroprevalence of antibodies developed via infection and/or vaccination was higher among participants with a higher educational level. Conclusions: Most adults have developed anti-SARS-CoV-2 antibodies, while most teenagers and children remain 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 socioeconomically disadvantaged groups, and to minimize spread among children.

Seroprevalence of anti-SARS-CoV-2 antibodies and cross-variant neutralization capacity after the Omicron BA.2 wave in Geneva, Switzerland

“…Between April 29 th and June 9 th , 2022, we recruited participants from a random sample of individuals aged ≥6 months provided by the cantonal population registry (Office cantonal de la population et des migrations), and from an age-and sex-stratified random sample of adults who participated in at least one of our previous serosurveys (Supplementary figure 2) (20)(21)(22). Newly selected individuals were invited by letter, while returning participants were invited by letter or email when available.…”

“…With a population of about 500000, the canton of Geneva, Switzerland, has had 261946 confirmed cases (448 per 1000 inhabitants) and 883 deaths reported by July 21 st , 2022 (19). Our previous serosurvey revealed that by June-July 2021, around two thirds of the population had developed anti-SARS-CoV-2 antibodies following vaccination and/or infection, half of which having antibodies of infection origin (20). Since then, eligibility for vaccination against COVID-19 has progressively expanded in Geneva to cover most age groups, including ages 12-15 years since June 2021 and ages 5-11 years since January 2022 (Supplementary figure 1).…”

Impacto de la pandemia en la atención primaria. Informe SESPAS 2022

“…Desde el inicio de la pandemia, en marzo de 2020, y hasta el momento en que se redacta este artículo, se han notificado alrededor de 10 millones de infectados, habiendo indicios de que la cifra real puede ser de incluso el doble 9 . En la figura 1 se 10 muestra la evolución de la tasa de incidencia acumulada a 14 días y de la tasa de mortalidad acumulada a 14 días, distinguiéndose seis ciclos de pandemia que, a efectos prácticos para este artículo, simplificamos en cuatro periodos en función de sus efectos sobre los valores nucleares antes descritos en la AP.…”

Clinical sensitivity and specificity of a high-throughput microfluidic nano-immunoassay combined with capillary blood microsampling for the identification of anti-SARS-CoV-2 Spike IgG serostatus

“…Considering an approximate prevalence of 25% at that stage in the pandemic [29], this would correspond to a positive predictive value (PPV) of 100%, a negative predictive value (NPV) of 86•06% and a diagnostic accuracy of 87•85%. Finally, the receiver operating characteristic curve (AUROC) is 0•9940 (95% CI: 0•9873-1•000) (Fig.…”