Search

The CELSPAC - FIREexpo biomonitoring study investigates the long-term effects of chemical exposure on firefighters' wellness and fitness. It aims to provide science-based measures to minimize the health risks of the firefighting occupation. Here, we present the study design, cohort profile, and first results with respect to internal per- and polyfluoroalkyl substances (PFAS) and polycyclic aromatic hydrocarbons (PAH) levels in study participants. Participants (n = 166) were divided into three subcohorts: i) newly recruited firefighters, ii) professional firefighters with several years' experience, and iii) the control group. Participants underwent physical performance tests, provided information on their lifestyle and diet, and urine and blood samples 1-4 times within an 11-week period. 12 serum PFAS and 10 urinary hydroxylated PAH (OH-PAH) levels were determined using HPLC-MS/MS and compared between subcohorts and samplings. The association of internal exposure with reported lifestyles and occupational factors was investigated using Spearman's correlation, principal component analysis, and multivariate regression analysis. ΣPFAS levels in firefighters were significantly higher than in the control group and were mostly associated with the length of firefighting career, age, blood donation, and population size. 10.9 % and 7.6 % of measurements exceeded the HBM-I or HBM-II value for PFOS and PFOA, respectively. Urinary ΣPAH levels increased significantly after training with burning wooden pallets, but none of them exceeded the no observed genotoxic effect level. Firefighters' occupational exposure, its sources, and pathways, need to be systematically monitored and investigated on a long-term and individual basis. The CELSPAC - FIREexpo study helps to clarify the degree of occupational exposure to the given compounds and the subsequent risks to firefighters.

Many legacy and emerging flame retardants (FRs) have adverse human and environmental health effects. This study reports legacy and emerging FRs in children from nine European countries from the HBM4EU aligned studies. Studies from Belgium, Czech Republic, Germany, Denmark, France, Greece, Slovenia, Slovakia, and Norway conducted between 2014 and 2021 provided data on FRs in blood and urine from 2136 children. All samples were collected and analyzed in alignment with the HBM4EU protocols. Ten halogenated FRs were quantified in blood, and four organophosphate flame retardants (OPFR) metabolites quantified in urine. Hex-abromocyclododecane (HBCDD) and decabromodiphenyl ethane (DBDPE) were infrequently detected (< 16% of samples). BDE-47 was quantified in blood from Greece, France, and Norway, with France (0.36 ng/g lipid) having the highest concentrations. BDE-153 and-209 were detected in < 40% of samples. Dechlorane Plus (DP) was quantified in blood from four countries, with notably high median concentrations of 16 ng/g lipid in Slovenian children. OPFR metabolites had a higher detection frequency than other halogenated FRs. Diphenyl phosphate (DPHP) was quantified in 99% of samples across 8 countries at levels similar to 5 times higher than other OPFR metabolites (highest median in Slovenia of 2.43 ng/g lipid). FR concentrations were associated with lifestyle factors such as cleaning frequency, employment status of the father of the household, and renovation status of the house, among others. The concentrations of BDE-47 in children from this study were similar to or lower than FRs found in adult matrices in previous studies, suggesting lower recent exposure and effectiveness of PBDE restrictions.

PurposeMonitoring the seroprevalence of COVID-19 antibodies is an important tool to design and adjust preventive strategies. We used prospective data on a large population sample with repeated IgG antibody measurement to examine changes in seropositivity before and during the national vaccination campaign in the Czech Republic.Methods22,130 persons provided blood samples for COVID-19 IgG antibody measurement at two time points approximately 5-7 months apart, between October 2020 and March 2021 (Phase 1, before vaccination), and between April and September 2021 (during vaccination campaign).ResultsBefore vaccination (Phase 1), seroprevalence increased from 15% in October 2020 to 56% in March 2021. By the end of Phase 2, in September 2021, prevalence increased to 91%; the highest seroprevalence was seen among vaccinated persons with and without previous SARS-CoV-2 infection (99.7% and 97.2%, respectively), while the lowest seroprevalence was found among unvaccinated persons with no signs of disease (26%). Vaccination rates were lower in persons who were seropositive in phase 1 but increased with age and body mass index. Only 9% of unvaccinated subjects who were seropositive in phase 1 became seronegative by phase 2.ConclusionThe rapid increase in seropositivity during the 2nd wave of the COVID-19 epidemic (covered by phase 1 of this study) was followed by a similarly steep rise in seroprevalence during the national vaccination campaign, reaching seropositivity rates of over 97% among vaccinated persons.

The pre- and perinatal environment is thought to play a critical role in shaping brain development. Specifically, maternal mental health and maternal care have been shown to influence offspring brain development in regions implicated in emotional regulation such as the amygdala. In this study, we used data from a neuroimaging follow-up of a prenatal birth-cohort, the European Longitudinal Study of Pregnancy and Childhood, to investigate the impact of early postnatal maternal anxiety/co-dependence, and prenatal and early-postnatal depression and dysregulated mood on amygdala volume and morphology in young adulthood (n = 103). We observed that in typically developing young adults, greater maternal anxiety/co-dependence after birth was significantly associated with lower volume (right: t = -2.913, p = 0.0045, β = -0.523; left: t = -1.471, p = 0.144, β = -0.248) and non-significantly associated with surface area (right: t = -3.502, q = 0.069,10%FDR, β = -0.090, left: t = -3.137, q = 0.117,10%FDR, = -0.088) of the amygdala in young adulthood. Conversely, prenatal maternal depression and mood dysregulation in the early postnatal period was not associated with any volumetric or morphological changes in the amygdala in young adulthood. Our findings provide evidence for subtle but long-lasting alterations to amygdala morphology associated with differences in maternal anxiety/co-dependence in early development.

Objective:Dietary pattern analysis constitutes a suitable method for identifying complex food preferences as well as a useful tool for comparing dietary behaviour across individual populations. In addition to a lack of information on Central European dietary patterns, dietary data featuring a longitudinal aspect are likewise largely unavailable for the region. Our study thus strives to address this gap by analysing children’s dietary patterns, their stability and possible changes at 7, 11 and 15 years in the Czech part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC–CZ).Design:We analysed dietary data based on the self-reported semi-quantitative FFQ obtained in 1998, 2002 and 2006. Dietary patterns were derived using factor analysis for each period, followed by the determination of dietary pattern stability across the individual periods.Setting:The analysis of dietary patterns was based on longitudinal children’s dietary data from the geographical region that was undergoing massive socio-economic changes at the time of birth of the study subjects.Participants:All participants were children. At 7 years the analysis included 3220 children, at 11 years the analysis included 2509 children and at 15 years the analysis included 1589 children.Results:Two stable children’s dietary patterns labelled as ‘prudent’ and ‘junk food’ were identified across all three time points (7, 11 and 15 years).Conclusions:This study identifies stable longitudinal trends in the dietary behaviour of children enrolled in the ELSPAC-CZ study.

In 54 participants (41% women) from the Czech arm of the European Longitudinal Study of Pregnancy and Childhood, a national birth cohort with prospectively collected data from their birth until young adulthood, we aimed to study the association between early-life socioeconomic deprivation (ELSD), cognitive ability in adolescence, trait anxiety and resting state functional connectivity of the lateral prefrontal cortex (LPFC) in young adulthood. We found that ELSD was associated with lower cognitive ability in adolescence (at age 13) as well as higher trait anxiety in young adulthood (at age 23/24). Higher cognitive ability in adolescence predicted lower trait anxiety in young adulthood. Resting state functional connectivity between the right LPFC and a cluster of voxels including left precentral gyrus, left postcentral gyrus and superior frontal gyrus mediated the relationship between lower cognitive ability in adolescence and higher trait anxiety in young adulthood. These findings indicate that lower cognitive ability and higher trait anxiety may be both consequences of socioeconomic deprivation in early life. The recruitment of the right LPFC may be the underlying mechanism, through which higher cognitive ability may ameliorate trait anxiety.

Humans are widely exposed to phthalates and their novel substitutes, and considering the negative health effects associated with some phthalates, it is crucial to understand population levels and exposure determinants. This study is focused on 300 urine samples from teenagers (aged 12-17) and 300 from young adults (aged 18-37) living in Czechia collected in 2019 and 2020 to assess 17 plasticizer metabolites as biomarkers of exposure. We identified widespread phthalate exposure in the study population. The diethyl phthalate metabolite monoethyl phthalate (MEP) and three di (2-ethylhexyl) phthalate metabolites were detected in the urine of >99% of study participants. The highest median concentrations were found for metabolites of low-molecular-weight (LMW) phthalates: mono-n-butyl phthalate (MnBP), monoisobutyl phthalate (MiBP) and MEP (60.7; 52.6 and 17.6 μg/L in young adults). 1,2-cyclohexanedicarboxylic acid diisononyl ester (DINCH) metabolites were present in 68.2% of the samples with a median of 1.24 μg/L for both cohorts. Concentrations of MnBP and MiBP were similar to other European populations, but 5-6 times higher than in populations in North America. We also observed large variability in phthalate exposures within the study population, with 2-3 orders of magnitude differences in urinary metabolites between high and low exposed individuals. The concentrations varied with season, gender, age, and lifestyle factors. A relationship was found between high levels of MEP and high overall use of personal care products (PCPs). Cluster analysis suggested that phthalate exposures depend on season and multiple lifestyle factors, like time spent indoors and use of PCPs, which combine to lead to the observed widespread presence of phthalate metabolites in both study populations. Participants who spent more time indoors, particularly noticeably during colder months, had higher levels of high-molecular weight phthalate metabolites, whereas participants with higher PCP use, particularly women, tended to have higher concentration of LMW phthalate metabolites. Authors thank the Research Infrastructure RECETOX RI (No. LM2018121) and CETOCOEN EXCELLENCE (CZ.02.1.01/0.0/0.0/17_043/0009632) for a supportive background. The work was supported by the Operational Programme Research, Development and Innovation – project Cetocoen Plus (CZ.02.1.01/0.0/0.0/15_003/0000469) and the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 857560. This study has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 733032. We thank all collaborating field workers, laboratory and administrative personnel, and especially the cohort participants who invested their time and provided samples and information for this study. This study reflects only the authors’ view and the European Commission is not responsible for any use that may be made of the information it contains. Sí

Background: Although the Czech Republic weathered the first wave of the COVID-19 epidemic with relatively low incidence, the second wave of the global pandemic saw it rank among countries bearing the greatest COVID-19 burden, both in Europe and on a worldwide scale. The aim of the nationwide prospective seroconversion (PROSECO) study was to investigate the dynamics of seroconversion of anti-SARS-CoV-2 IgG antibodies in the Czech population. Methods: All clients of the second largest health insurance company in the Czech Republic were sent a written invitation to participate in this longitudinal study. The study includes the first 30,054 persons who provided a blood sample between October 2020 and March 2021. Seroprevalence was compared between calendar periods of blood sample collection, RT-PCR test results, sociodemographic factors, and other characteristics. Findings: The data show a dramatic increase in seropositivity over time, from 28% in October/November 2020 to 43% in December 2020/January 2021 to 51% in February/March 2021. These trends were consistent with government data on cumulative viral antigenic prevalence in the population captured by PCR testing – although the seroprevalence rates established in this study were considerably higher than those listed in government data. Data pooled across the entire study period exhibited minor differences in seropositivity between sexes, age groups and body mass index categories; results were similar between test providing laboratories. Seropositivity was substantially higher among symptomatic vs. asymptomatic persons (76% vs. 34%). At least one third of all seropositive participants were asymptomatic, and 28% participants who developed antibodies against SARS-CoV-2 never underwent PCR testing. Interpretation: Antibody response provides a better marker of past SARS-CoV-2 infection than PCR testing data. Our data on seroconversion confirm the rapidly increasing prevalence in the Czech population during the dramatically rising pandemic wave prior to the beginning of massive vaccination. The planned second and third assessment of the study participants (April 2021 – September 2021, October 2021 – March 2022) will provide valuable evidence on the seroprevalence changes following vaccination and persistence of antibodies resulting from natural infection and vaccination. Funding: Prevention Programme of the Health Insurance Company of the Ministry of the Interior of the Czech Republic, Ministry of Education, Youth and Sport of the Czech Republic, EU Horizon 2020, European Structural and Investment Funds. Declaration of Interest: We declare no competing interests. Ethical Approval: This study received approval from the ELSPAC ethics committee under reference number (C)ELSPAC/EK/5/2021.

Experience of early-life socioeconomic deprivation (ELSD) may increase the risk of mental disorders in young adulthood. This association may be mediated by structural and functional alterations of the hippocampus.We conducted a prospective cohort study on 122 participants of the European Longitudinal Study of Pregnancy and Childhood. Information about ELSD was collected via questionnaire from mothers during the first 18 months of participants' lives. At age 23-24, participants underwent examination by structural magnetic resonance imaging, resting-state functional connectivity and assessment of depressive symptoms (Mood and Feelings Questionnaire) and anxiety (Spielberger State-Trait Anxiety Inventory). The association of ELSD with brain outcomes in young adulthood was assessed with correlations, linear regression (adjusting for sex, socioeconomic position and mother's mental health) and moderated mediation analysis.Higher ELSD was associated with greater depressive symptoms (Early preventive strategies targeted at children from socioeconomically deprived families may yield long-lasting benefits for the mental health of the population.

Highlights • In young adult women, slower epigenetic clock predicted less symptoms of anxiety. • In young adult women, slower epigenetic clock predicted greater cortical GM volume. • This effect of epigenetic clock in young adult women was largest in frontal lobe. • The link of epigenetic clock and anxiety was mediated by GM volume in frontal lobe. • No similar relationships were found in young adult men or adolescents., DNA methylation changes consistently throughout life and age-dependent alterations in DNA methylation can be used to estimate one’s epigenetic age. Post-mortem studies revealed higher epigenetic age in brains of patients with major depressive disorder, as compared with controls. Since MDD is highly correlated with anxiety, we hypothesized that symptoms of anxiety, as well as lower volume of grey matter (GM) in depression-related cortical regions, will be associated with faster epigenetic clock in a community-based sample of young adults. Participants included 88 young adults (53% men; 23–24 years of age) from the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) who participated in its neuroimaging follow-up and provided saliva samples for epigenetic analysis. Epigenetic age was calculated according to Horvath (Horvath, 2013). Women had slower epigenetic clock than men (Cohen’s d = 0.48). In women (but not men), slower epigenetic clock was associated with less symptoms of anxiety. In the brain, women (but not men) with slower epigenetic clock had greater GM volume in the cerebral cortex (brain size-corrected; R2 = 0.07). Lobe-specific analyses showed that in women (but not men), slower epigenetic clock was associated with greater GM volume in frontal lobe (R2 = 0.16), and that GM volume in frontal lobe mediated the relationship between the speed of epigenetic clock and anxiety trait (ab = 0.15, SE = 0.15, 95% CI [0.007; 0.369]). These findings were not replicated, however, in a community-based sample of adolescents (n = 129; 49% men; 12–19 years of age), possibly due to the different method of tissue collection (blood vs. saliva) or additional sources of variability in the cohort of adolescents (puberty stages, socioeconomic status, prenatal exposure to maternal smoking during pregnancy).

Depression is the leading cause of years lost due to disability worldwide. Still, the mechanisms underlying its development are not well understood. This study aimed to evaluate white-matter properties associated with depressive symptomatology in young adulthood and their developmental origins. Diffusion tensor imaging and assessment of depressive symptomatology were conducted in 128 young adults (47% male, age 23-24) from a prenatal birth cohort (European Longitudinal Study of Pregnancy and Childhood). For a subset of these individuals, the database included information on prenatal stress (n = 93) and depressive symptoms during adolescence (assessed repeatedly at age 15 and 19). Depressive symptoms in young adulthood were associated with lower fractional anisotropy in the left and right cingulum and higher fractional anisotropy in the right corticospinal tract and superior longitudinal fasciculus. Further analyses revealed that prenatal stress and depressive symptomatology during adolescence were independent predictors of altered white-matter properties in the cingulum in young adulthood. We conclude that typically developing young adults with more depressive symptoms already exhibit tract-specific alterations in white-matter properties and that prenatal stress and depressive symptomatology during adolescence might contribute to their development.

Background The relationship between low iodine status and pregnancy-associated comorbidities has been known for decades. The relationship between iodine intake and placental pathologies is, however, far less clear. This study was designed to examine the relationship between dietary iodine intake and placental size while also focusing on typical adverse pregnancy outcomes. Method The dietary iodine intake of 4711 pregnant women enrolled in the Czech part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC) in 1990–1991 was established using a 145-item food frequency questionnaire. Multivariate linear regression models were used to estimate the relationship between dietary iodine intake during pregnancy and placental weight. Additional models were constructed to investigate the relationship between estimated dietary iodine intake and adverse birth outcomes. Results The estimated average iodine intake in the ELSPAC cohort was 106.6 μg/day. In the fully adjusted model, estimated dietary iodine intake was found to be significantly negatively associated with placental weight (β = −0.025, 95% CI: -0.044; −0.006, p = 0.011). Moreover, estimated dietary iodine intake was found to be significantly positively associated with the birth weight / placental weight ratio in the fully adjusted model (β = −0.024, 95% CI: 0.004; 0.043, p = 0.016). Conclusions This study provides evidence of a relationship between estimated dietary iodine intake and placental weight and the birth weight / placental weight ratio. Additional research is warranted to provide more insight into the role of iodine in early as well as late placentation.

Little is currently known about the relationship between the parental diet during pregnancy and the growth of the child from early childhood until early adulthood. This study was designed to examine whether the dietary patterns of the parents during a pregnancy and of the respective child at 3 years are associated with the length/height-for-age z-score of child at birth, 3 years of age and at 19 years of age.Dietary patterns of pregnant women and their partners, and offspring at 3 years that were enroled in the 1990-1991 period in the Czech part of the European Longitudinal Study of Pregnancy and Childhood. Multivariable linear regression models were used to estimate the relationship between the dietary patterns of parents (835 child-mother-father trios) during pregnancy and the length/height-for-age z-score of their offspring at birth, 3 years and 19 years.The maternal health-conscious food pattern was found to predict lower child height at 3 years, but not at birth nor at 19 years of age. An increase in the health-conscious pattern score of the maternal diet was associated with significantly lower height-for-age z-score at 3 years; however, the observed effect lost its significance after the adjustment for diet of the child at 3 years.After full adjustment, the only significant predictors of the height-for-age z-score of the child at 3 years were the heights of both parents and maternal education. More research into the association of maternal diet in pregnancy and height of child is necessary.

BackgroundComparable evidence on adiposity inequalities in early life is lacking across a range of European countries. This study investigates whether low maternal education is associated with overweight and obesity risk in children from distinct European settings during early childhood. MethodsProspective data of 45 413 children from 11 European cohorts were used. Children's height and weight obtained at ages 4-7 years were used to assess prevalent overweight and obesity according to the International Obesity Task Force definition. The Relative/Slope Indices of Inequality (RII/SII) were estimated within each cohort and by gender to investigate adiposity risk among children born to mothers with low education as compared to counterparts born to mothers with high education. Individual-data meta-analyses were conducted to obtain aggregate estimates and to assess heterogeneity between cohorts. ResultsLow maternal education yielded a substantial risk of early childhood adiposity across 11 European countries. Low maternal education yielded a mean risk ratio of 1.58 (95% confidence interval (CI) 1.34, 1.85) and a mean risk difference of 7.78% (5.34, 10.22) in early childhood overweight, respectively, measured by the RII and SII. Early childhood obesity risk by low maternal education was as substantial for all cohorts combined (RII = 2.61 (2.10, 3.23)) and (SII = 4.01% (3.14, 4.88)). Inequalities in early childhood adiposity were consistent among boys, but varied among girls in a few cohorts. ConclusionsConsiderable inequalities in overweight and obesity are evident among European children in early life. Tackling early childhood adiposity is necessary to promote children's immediate health and well-being and throughout the life course.

This study aimed to determine whether prenatal stress, measured by the number of stressful life events during the first 20 weeks of pregnancy, might relate to mood dysregulation and altered brain structure in young adulthood. Participants included 93 young adults from a community-based birth cohort from the Czech Republic. Information on prenatal stress exposure was collected from their mothers in 1990-1992. Magnetic resonance imaging (MRI) and mood-related data were collected from the young adults in 2015. MRI analyses focused on overall gray matter (GM) volume and GM volume of cortical regions previously associated with major depression. Higher prenatal stress predicted more mood dysregulation, lower overall GM volume, and lower GM volume in mid-dorsolateral frontal cortex, anterior cingulate cortex, and precuneus in young adulthood. We observed no prenatal stress by sex interactions for any of the relations. We conclude that prenatal stress is an important risk factor that relates to worse mood states and altered brain structure in young adulthood irrespective of sex. Our results point to the importance and long-lasting effects of prenatal programming and suggest that offspring of mothers who went through substantial stress during pregnancy might benefit from early intervention that would reduce the odds of mental illness in later life.

Objectives: The study examined appearance and body satisfaction in adolescents. For these purposes, data from the European Longitudinal Study of Pregnancy and Childhood in the Czech Republic were used. Methods: The data were collected in 2010 and the sample comprised 3,105 18-year-old respondents. Results: The research found that the respondents who wished to reduce their weight were mostly women with BMI in the normal range. Based on the body cathexis scale, we found that women compared to men are more critical of stomach, hips, buttocks, and thighs, as well as overall weight and figure. The results showed that criticism of their weight from their immediate environment is unpleasant to both female and male adolescents to such an extent that it makes them try to reduce it. However, it is clear that girls are altogether less satisfied with their bodies than boys. Conclusion: For both genders, body dissatisfaction is most likely enhanced by critical comments from peers and parents about appearance, body weight etc.

The Czech ELSPAC study was set up as a part of the European Longitudinal Study of Pregnancy and Childhood (ELSPAC). ELSPAC was designed as a population-based prospective longitudinal birth cohort study to investigate the effects of biological, psychosocial, economic and environmental factors on pregnancy, delivery and subsequent child´s development and health. The study was initiated by the World Health Organization (WHO) Regional Office for Europe in 1985, with the aim to enrol 40 000 children across Europe. Seven independent centres—ALSPAC, Isle of Man, the Czech Republic, Slovakia, Ukraine, Greece and Russia—joined the project, coordinated by Professor Golding at Bristol University, UK. The coordination centre was also responsible for most of the protocol development, including follow-up planning and questionnaire design. Enrolment of the Czech participants started in 1991. In addition to the primary aims of ELSPAC, the Czech team was interested also in the effects of the profound socioeconomic changes related to the societal transformation after the fall of Communism in 1989.

Cucumber (Cucumis sativus L.) cytokinin-independent embryogenic cell suspension cultures were derived and maintained for more than 3.5 years without losing the embryogenic potential. The preparation and the characteristics of the cucumber embryogenic cell suspension possess many similarities to that of carrot. The cultures were induced from hypocotyl explants of in vitro grown cucumber plants in liquid MS media containing 2,4-dichlorophenoxyacetic acid as the sole growth regulator during 6 weeks and they contained a heterogeneous array of several different types of single cells and cell clusters (PEMs). The established cell suspensions were subcultured in 1-week interval, while the inoculation density was optimized to 2.0 × 105 cells ml−1 using cell viability as a marker. Somatic embryos were obtained after the transfer of the proembryogenic masses to a hormone-free semisolid MS medium with a frequency of 388 ± 57 somatic embryos per 1 ml of packed cell volume of the established cucumber embryogenic culture within 7 days. The frequency of normal somatic embryos with two cotyledons was found to be 78%. Such embryos possessed the potential of spontaneous maturation and the embryo conversion rates were 87%. The yield of normally growing plants was much higher compared with that previously described for cucumber systems. Somatic embryo-derived plants were successfully transferred to the greenhouse where they flowered and fruited.

ObjectiveExamine changes in SARS-CoV-2 seropositivity before and during the national vaccination campaign in the Czech Republic.DesignProspective national population-based cohort study.SettingMasaryk University, RECETOX, Brno.Participants22 130 persons provided blood samples at two time points approximately 5–7 months apart, between October 2020 and March 2021 (phase I, before vaccination), and between April and September 2021 (during vaccination campaign).Outcome measuresAntigen-specific humoral immune response was analysed by detection of IgG antibodies against the SARS-CoV-2 spike protein by commercial chemiluminescent immunoassays. Participants completed a questionnaire that included personal information, anthropometric data, self-reported results of previous RT-PCR tests (if performed), history of symptoms compatible with COVID-19 and records of COVID-19 vaccination. Seroprevalence was compared between calendar periods, previous RT-PCR results, vaccination and other individual characteristics.ResultsBefore vaccination (phase I), seroprevalence increased from 15% in October 2020 to 56% in March 2021. By the end of phase II, in September 2021, prevalence increased to 91%; the highest seroprevalence was seen among vaccinated persons with and without previous SARS-CoV-2 infection (99.7% and 97.2%, respectively), while the lowest seroprevalence was found among unvaccinated persons with no signs of disease (26%). Vaccination rates were lower in persons who were seropositive in phase I but increased with age and body mass index. Only 9% of unvaccinated subjects who were seropositive in phase I became seronegative by phase II.ConclusionsThe rapid increase in seropositivity during the second wave of the COVID-19 epidemic (covered by phase I of this study) was followed by a similarly steep rise in seroprevalence during the national vaccination campaign, reaching seropositivity rates of over 97% among vaccinated persons.