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BackgroundMore than two years into the COVID-19 pandemic, it is generally assumed that most of the population has developed anti-SARS-CoV-2 antibodies from infection and/or vaccination. However, public health decision-making is hindered by the lack of up-to-date and precise characterization of the immune landscape in the population. We thus aimed to estimate anti-SARS-CoV-2 antibodies seroprevalence and cross-variant neutralization capacity after Omicron became dominant in Geneva, Switzerland. MethodsWe conducted a population-based serosurvey between April 29th and June 9th, 2022, recruiting children and adults of all ages from age-stratified random samples of the Geneva general population. Anti-SARS-CoV-2 antibody presence was assessed using commercial immunoassays targeting either the spike (S) or nucleocapsid (N) protein. Antibodies neutralization capacity against different SARS-CoV-2 variants was evaluated using a cell-free Spike trimer-ACE2 binding-based surrogate neutralization assay. Seroprevalence of anti-SARS-CoV-2 antibodies and neutralization capacity were estimated using Bayesian modeling frameworks accounting for the demographics, vaccination, and infection statuses of the Geneva population. ResultsAmong the 2521 individuals included in the analysis (55.2% women; 21.4% aged <18 years and 14.2% aged [≥] 65 years), overall seroprevalence of antibodies was 93.8% (95% credible interval: 93.1-94.5), including 72.4% (70.0-74.7) for infection-induced antibodies. Estimates of neutralizing antibodies based on a representative subsample of 1160 participants ranged from 79.5% (77.1-81.8) against the Alpha variant to 46.7% (43.0-50.4) against the Omicron BA.4/BA.5 subvariants. Despite having high seroprevalence of infection-induced antibodies (76.7% [69.7-83.0] for ages 0-5 years, 90.5% [86.5-94.1] for ages 6-11 years), children aged <12 years had substantially lower neutralizing activity than older participants, particularly against Omicron subvariants. In general, higher levels of neutralization activity against pre-Omicron variants were associated with vaccination, particularly having received a booster dose. Higher levels of neutralization activity against Omicron subvariants were associated with booster vaccination alongside recent infection. ConclusionMore than nine in ten individuals in the Geneva population have developed anti-SARS-CoV-2 antibodies through vaccination and/or infection, but less than half of the population has antibodies with neutralizing activity against the currently circulating Omicron BA.5 subvariant. Hybrid immunity obtained through booster vaccination and infection appears to confer the greatest neutralization capacity, including against Omicron.
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BackgroundSARS-CoV-2 infection and its health consequences have disproportionally affected disadvantaged socio-economic groups globally. This study aimed to analyze the association between socio-economic conditions and having developed anti-SARS-CoV-2 antibodies in a population-based sample in the canton of Geneva, Switzerland. MethodsData was obtained from a population-based serosurvey of adults in Geneva and their household members, between November and December, 2020, towards the end of the second pandemic wave in the canton. Participants were tested for anti-SARS-CoV-2 antibodies. Socio-economic conditions representing different dimensions were self-reported. Mixed effects logistic regressions were conducted for each predictor to test its association with seropositive status as the main outcome. Results2,889 adults completed the study questionnaire and were included in the final analysis. Retired participants and those living in suburban areas had lower odds of a seropositive result when compared to employed participants (OR 0.42, 95% CI - 0.20 - 0.87) and those living in urban areas (OR 0.67, 95% CI - 0.46 - 0.97), respectively. People facing financial hardship for less than a year had higher odds of a seropositive result compared to those who had never faced them (OR 2.23, 95% CI - 1.01 - 4.95). Educational level, occupational position and household income were not associated with being seropositive, nor were ethnicity or country of birth. DiscussionWhile traditional measures of socio-economic position did not seem to be related to the risk of being infected in this sample, this study sheds lights on the importance of examining the broader social determinants of health when evaluating the differential impact of the pandemic within the population.
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AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSBackgroundC_ST_ABSIt is now established that a significant proportion of adults experience persistent symptoms after SARS-CoV-2 infection. However, evidence for children and adolescents is still inconclusive. In this population-based study, we examine the proportion of children and adolescents reporting persistent symptoms after SARS-CoV-2 infection, as assessed by serological status, and compare this to a seronegative control group. MethodsWe conducted a serosurvey in June-July 2021, recruiting 660 children and adolescents from 391 households selected randomly from the Geneva population. We tested participants for anti-SARS-CoV-2 antibodies targeting the nucleocapsid (N) protein to determine previous infection. A parent filled a questionnaire including questions on COVID-19-related symptoms lasting at least 2 weeks. FindingsAmong children seropositive for anti-SARS-CoV-2 antibodies, the sex- and age-adjusted prevalence of symptoms lasting longer than two weeks was 18.3%, compared to 11.1% among seronegative children (prevalence difference ({Delta}aPrev)=7.2%, 95%CI:1.5-13.0). Main symptoms declared among seropositive children were fatigue (11.5%) and headache (11.1%). For 8.6% (aPrev, 95%CI: 4.7-12.5) of seropositives, these symptoms were declared to be highly limiting of daily activities. Adolescents aged 12-17 years had a higher adjusted prevalence of persistent symptoms (aPrev=29.1%, 95%CI:19.4-38.7) than younger children. Comparing seropositive and seronegative adolescents, the estimated prevalence of symptoms lasting over four weeks is 4.4% ({Delta}aPrev, 95%CI:-3.8-13.6). InterpretationA significant proportion of children aged 12 to 17 years had symptoms lasting over two weeks after SARS-CoV-2 infection, with an estimated prevalence of symptoms lasting over 4 weeks of 4.4% in this age group. This represents a large number of adolescents in absolute terms, and should raise concern in the context of unknown long-term evolution of symptoms. Younger children appear to experience long-lasting symptoms less frequently, as no difference was observed between the seropositive and seronegative sample. Further studies with larger samples sizes are needed. FundingSwiss Federal Office of Public Health, Geneva General Directorate of Health, HUG Private Foundation, SSPH+, Fondation des Grangettes.
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BackgroundUp-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. MethodsWe 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). ResultsWe 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). 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. ConclusionsMost 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.
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ObjectiveThis study aimed to assess acceptance of COVID-19 vaccination as well as its sociodemographic and clinical determinants in a general population sample three months after the launch of the vaccination program in Switzerland. MethodsIn March 2021, an online questionnaire on vaccination acceptance was proposed to adults included in a longitudinal cohort study of previous population-based serosurveys carried out in the canton of Geneva. Questions were asked about COVID-19 vaccination acceptance, reasons of acceptance or refusal, and attitudes about vaccination in general. Data on demographic (age, sex, education, income, professional status, living conditions) and health-related characteristics (having a chronic disease, COVID-19 diagnosis, smoking status) were assessed at inclusion in the cohort (December 2020). ResultsOverall, 4067 participants (completion rate of 77.4%) responded to the survey between March 17 and April 1, 2021. The mean age of respondents was 53.3 years and 56.0% were women. Most had completed tertiary education (64.7%) and over 60% were currently professionally active. At the time of the survey, 17.2% of respondents had already been vaccinated with at least one dose or had made an appointment to get vaccinated, and an additional 58.5% intended or rather intended to get vaccinated. The overall acceptance of COVID-19 vaccination was 75.7%, with a higher acceptance among men compared to women, older adults compared to younger adults, high-income individuals compared to those with a low income, participants living in urban and semi-urban areas compared to rural, and retirees and students compared to employed individuals. Acceptance was lower among individuals having completed apprenticeships and secondary education compared to those with tertiary education. The most common reasons reported by participants intending to get vaccinated were the desire to get back to normal, to protect themselves, their community and/or society, and their relatives or friends against the risk of infection by SARS-CoV-2, as well as the desire to travel. Less than half (45.6%) of participants having children were willing or rather willing to have their children vaccinated against COVID-19 if it were recommended by public health authorities. ConclusionAlthough our study found a 75.7% acceptance of COVID-19 vaccination, there were noticeable socio-demographic disparities in vaccination acceptance. These data will be useful for public health measures targeting hesitant populations when developing health communication strategies. These results will be updated over time with a new release of the survey in autumn 2021.