Deep profiling of antigen-specific B cells from different pathogens identifies novel compartments in the IgG memory B cell and antibody-secreting cell lineages (preprint)

A better understanding of the bifurcation of human B cell differentiation into memory B cells (MBC) and antibody-secreting cells (ASC) and identification of MBC and ASC precursors is crucial to optimize vaccination strategies or block undesired antibody responses. To unravel the dynamics of antigen-induced B cell responses, we compared circulating B cells reactive to SARS-CoV-2 (Spike, RBD and Nucleocapsid) in COVID-19 convalescent individuals to B cells specific to Influenza-HA, RSV-F and TT, induced much longer ago. High-dimensional spectral flow cytometry indicated that the decision point between ASC- and MBC-formation lies in the CD43+CD71+IgG+ Activated B cell compartment, showing properties indicative of recent germinal center activity and recent antigen encounter. Within this Activated B cells compartment, CD86+ B cells exhibited close phenotypical similarity with ASC, while CD86- B cells were closely related to IgG+ MBCs. Additionally, different activation stages of the IgG+ MBC compartment could be further elucidated. The expression of CD73 and CD24, regulators of survival and cellular metabolic quiescence, discerned activated MBCs from resting MBCs. Activated MBCs (CD73-CD24lo) exhibited phenotypical similarities with CD86- IgG+ Activated B cells and were restricted to SARS-CoV-2 specificities, contrasting with the resting MBC compartment (CD73-/CD24hi) that exclusively encompassed antigen-specific B cells established long ago. Overall, these findings identify novel stages for IgG+ MBC and ASC formation and bring us closer in defining the decision point for MBC or ASC differentiation. ImportanceIn this study, researchers aimed to better understand human B cell differentiation and their role in establishing long-lived humoral immunity. Using high-dimensional flow cytometry, they studied B cells reactive to three SARS-CoV-2 antigens in individuals convalescent for COVID-19, and compared their phenotypes to B cells reactive to three distinct protein antigens derived from vaccines or viruses encountered months to decades before. Their findings showed that Activated B cells reflect recent germinal center graduates that may have diverse fates; with some feeding the pool of antibody-secreting cells and others fueling the resting memory B cell compartment. Activated B cells gradually differentiate into resting memory B cells through an activated MBC phase. Increased expression of the cellular metabolic regulators CD73 and CD24 in resting memory B cells distinguishes them from the activated memory B cells phase, and is likely involved in sustaining a durable memory of humoral immunity. These findings are crucial for the development of vaccines that provide lifelong protection and may show potential to define reactive B cells in diseases where the cognate-antigen is still unknown such as in autoimmunity, cancers, or novel viral outbreaks.

Inflammatory profiles are associated with long COVID up to 6 months after illness onset: a prospective cohort study of individuals with mild to critical COVID-19 (preprint)

Background After initial COVID-19 disease, immune dysregulation may persist and drive post-acute sequelae of COVID-19 (PASC). We described longitudinal trajectories of cytokines in adults up to 6 months following SARS-CoV-2 infection and explored early predictors of PASC. Methods RECoVERED is a prospective cohort of individuals with laboratory-confirmed SARS-CoV-2 infection between May 2020 and June 2021 in Amsterdam, the Netherlands. Serum was collected at weeks 4, 12 and 24 of follow-up. Monthly symptom questionnaires were completed from month 2 after illness onset onwards; lung diffusion capacity (DLCO) was tested at 6 months. Cytokine concentrations were analysed by human magnetic Luminex screening assay. We used a linear mixed-effects model to study log-concentrations of cytokines over time, assessing their association with socio-demographic and clinical characteristics that were included in the model as fixed effects. Results 186/349 (53%) participants had [≥]2 serum samples and were included. Of these, 101 (54%: 45/101[45%] female, median age 55 years [IQR=45-64]) reported PASC at 12 and 24 weeks after illness onset. We included 37 reference samples (17/37[46%] female, median age 49 years [IQR=40-56]). PASC was associated with raised CRP and abnormal diffusion capacity with raised IL10, IL17, IL6, IP10 and TNF at 24 weeks in the multivariate model. Early (0-4 week) IL-1{beta} and BMI at illness onset were predictive of PASC at 24 weeks. Conclusions Our findings indicate that immune dysregulation plays an important role in PASC pathogenesis, especially among those individuals with reduced pulmonary function. Early IL-1{beta} shows promise as predictors of PASC.

Antibodies against SARS-CoV-2 control complement-induced inflammatory responses to SARS-CoV-2 (preprint)

Dysregulated immune responses contribute to pathogenesis of COVID-19 leading to uncontrolled and exaggerated inflammation observed during severe COVID-19. However, it remains unclear how immunity to SARS-CoV-2 is induced and subsequently controlled. Notably, here we have uncovered an important role for complement in the induction of innate and adaptive immunity to SARS-CoV-2. Complement rapidly opsonized SARS-CoV-2 via the lectin pathway. Complement-opsonized SARS-CoV-2 efficiently interacted with dendritic cells (DCs), inducing type I IFN and pro-inflammatory cytokine responses, which were inhibited by antibodies against the complement receptors (CR)3 and CR4. These data suggest that complement is important in inducing immunity via DCs in the acute phase against SARS-CoV-2. Strikingly, serum from COVID-19 patients as well as monoclonal antibodies against SARS-CoV-2 attenuated innate and adaptive immunity induced by complement-opsonized SARS-CoV-2. Blocking the FcyRII, CD32, restored complement-induced immunity. These data strongly suggest that complement opsonization of SARS-CoV-2 is important for inducing innate and adaptive immunity to SARS-CoV-2. Subsequent induction of antibody responses is important to limit the immune responses and restore immune homeostasis. These data suggest that dysregulation in complement and FcyRII signalling might underlie mechanisms causing severe COVID-19.

Ethnic inequalities in incidence, nature, determinants, and duration of long COVID among hospitalised adults in the Netherlands: A retrospective cohort study (preprint)

Background In-depth data on long-term health effects of COVID-19 across ethnic groups are lacking. We investigated incidence, nature, determinants, and duration of long COVID across ethnic groups admitted for COVID-19 (Dutch, Turkish, Moroccan, African Surinamese, Asian Surinamese, Others) in the Netherlands.Methods We used COVID-19 admissions and follow up data (January 2021- July 2022) from Amsterdam University Medical Centers. We calculated incidence proportions of long COVID according to NICE guidelines by ethnic group (at twelve weeks post-discharge) and assessed its determinants in the total population via backward stepwise Poisson regressions. We then examined associations between ethnicity and long COVID using Poisson regression models and adjusted for derived determinants. We also assessed persistence (proportions) of long COVID symptoms at one-year post-discharge.Results 1886 participants were included. Long COVID incidence proportion was 26%, 95% CI 24–28%. Age and sex adjusted long COVID incidence proportions were highest in Surinamese, Turkish and Moroccan origin populations. Symptoms such as dizziness, joint and muscle pain, palpitations, insomnia, and headache varied by ethnicity. Determinants of long COVID were female sex, intensive care unit (ICU) admission, receiving oxygen, or corticosteroid therapy during admission. African Surinamese (IRR = 1.47, 95% CI:1.15–1.89), South-Asian Surinamese (IRR = 1.59, 1.11–2.26), Moroccan (IRR = 1.39, 1.05–1.83) and Turkish (IRR = 1.56, 1.12–2.18) had a higher risk of long COVID than Dutch origin after adjustments for sex, admission to intensive care unit ICU, and receiving oxygen and corticosteroid therapy during admission. Only 14% of any long COVID symptoms resolved by one-year post-discharge mainly among the South Asian Surinamese origin participants.Conclusion Our findings show that one fourth of participants report ongoing symptoms 12 weeks after a COVID-19 admission, with Surinamese, Moroccan and Turkish origin participants having higher long COVID risk than Dutch origin participants. Long COVID risk in the total population is related to female sex, ICU admission, and receiving oxygen and steroid therapies during hospitalisation. Majority of long COVID symptoms disappear within a year of hospital discharge. There is an urgent need for preventive and treatment efforts that consider ethnic inequalities in long COVID among hospitalised individuals.

Selection of long COVID symptoms influences prevalence estimates in a prospective cohort (preprint)

Background: Studies on long COVID differ in the selection of symptoms used to define the condition. We aimed to assess to what extent symptom selection impacts prevalence estimates of long COVID. Methods: In a prospective cohort of patients who experienced mild to critical coronavirus disease 2019 (COVID-19), we used longitudinal data on the presence of 20 different symptoms to evaluate changes in the prevalence of long COVID over time when altering symptom selection. Results: Changing symptom selection resulted in wide variation in long COVID prevalence, even within the same study population. Long COVID prevalence at 12 months since illness onset ranged from 39.6% (95%CI=33.4-46.2) when using a limited selection of symptoms to 80.6% (95%CI=74.8-85.4) when considering any reported symptom to be relevant. Conclusions: Comparing the occurrence of long COVID is already complex due to heterogeneity in study design and population. Disparate symptom selection may further hamper comparison of long COVID estimates between populations. Harmonised data collection tools could be one means to achieve greater reproducibility and comparability of results.

Low prevalence of current and past SARS-CoV-2 infections among visitors and staff members of homelessness services in Amsterdam at the end of the second wave of infections in the Netherlands (preprint)

Background People experiencing homelessness (PEH) may be at increased risk of SARS-CoV-2 infection and severe COVID-19. The Dutch government established emergency shelters and introduced preventive measures for homelessness services and there were no major SARS-CoV-2 outbreak noticed among PEH during the first two waves of infections. This study aimed to assess the prevalence of current and past infections among PEH and staff at the end of the second COVID-19 wave by conducting an on-site COVID-19 screening project at homelessness services in Amsterdam, the Netherlands. Methods We assessed the proportion of visitors and staff members of four homelessness services at two locations in Amsterdam with positive SARS-CoV-2 qPCR and antibody results (IgG/IgM Rapid Test, Biozek) in May 2021. We also assessed sociodemographic, clinical and lifestyle characteristics, compliance with basic prevention measures and intention to vaccinate against COVID-19 among PEH and staff.Results A total of 138 visitors and 53 staff members filled out a questionnaire and were tested. Among PEH, the SARS-CoV-2 positivity rate was 0% (0/133;95%CI=0-1.9) and the antibody positivity rate was 1.6% (2/131;95%CI=0.8-7.5). Among staff, these percentages were 3% (1/32;95%CI=0.1-16.2) and 11% (5/53;95%CI=3.6-23.6), respectively. Most participants were frequently compliant with the basic preventive measures ‘not shaking hands’, ‘wearing a face mask’ and ‘washing hands’, but not with ‘physical distancing’. Overall, intention to vaccinate for COVID-19 was low (30% for visitors, 10% for staff) or medium (28% for visitors, 35% for staff). Trust in COVID-19 policies were also, for the most part, low (27% for visitors, 17% for staff) or neutral (32% for visitors, 53% for staff).Conclusions We observed a low prevalence of past and current SARS-CoV-2 infections among PEH, which may be explained by instated shelter policies, limited daily activities of PEH and compliance with certain prevention measures. Vaccine hesitancy and mistrust among visitors and staff could hinder vaccination uptake, suggesting that improvements in public heath communication and interventions towards visitors and staff of homelessness services are needed.

Impacts of the COVID-19 pandemic on future seasonal influenza epidemics (preprint)

Summary Seasonal influenza viruses typically cause annual epidemics worldwide infecting 5-15% of the human population 1 . However, during the first two years of the COVID-19 pandemic, seasonal influenza virus circulation was unprecedentedly low with very few reported infections 2 . The lack of immune stimulation to influenza viruses during this time, combined with waning antibody titres to previous influenza virus infections, could lead to increased susceptibility to influenza in the coming seasons and to larger and more severe epidemics when infection prevention measures against COVID-19 are relaxed 3,4 . Here, based on serum samples from 165 adults collected longitudinally before and during the pandemic, we show that the waning of antibody titres against seasonal influenza viruses during the first two years of the pandemic is likely to be negligible. Using historical influenza virus epidemiological data from 2003-2019, we also show that low country-level prevalence of each influenza subtype over one or more years has only small impacts on subsequent epidemic size. These results suggest that the risks posed by seasonal influenza viruses remained largely unchanged during the first two years of the COVID-19 pandemic and that the sizes of future seasonal influenza virus epidemics will likely be similar to those observed before the pandemic.

Mapping the antigenic diversification of SARS-CoV-2 (preprint)

Large-scale vaccination campaigns have prevented countless SARS-CoV-2 infections, hospitalizations and deaths. However, the emergence of variants that escape from immunity challenges the effectiveness of current vaccines. Given this continuing evolution, an important question is when and how to update SARS-CoV-2 vaccines to antigenically match circulating variants, similar to seasonal influenza viruses where antigenic drift necessitates periodic vaccine updates. Here, we studied SARS-CoV-2 antigenic drift by assessing neutralizing activity against variants-of-concern (VOCs) of a unique set of sera from patients infected with a range of VOCs. Infections with ancestral or Alpha strains induced the broadest immunity, while individuals infected with other VOCs had more strain-specific responses. Omicron was substantially resistant to neutralization by sera elicited by all other variants. Antigenic cartography revealed that all VOCs preceding Omicron belong to one antigenic cluster, while Omicron forms a new antigenic cluster associated with immune escape and likely requiring vaccine updates to ensure vaccine effectiveness.

Four SARS-CoV-2 vaccines induce quantitatively different antibody responses against SARS-CoV-2 variants (preprint)

BackgroundEmerging and future SARS-CoV-2 variants may jeopardize the effectiveness of vaccination campaigns. Therefore, it is important to know how the different vaccines perform against diverse SARS-CoV-2 variants. MethodsIn a prospective cohort of 165 SARS-CoV-2 naive health care workers, vaccinated with either one of four vaccines (BNT162b2, mRNA-1273, AZD1222 or Ad26.COV2.S), we performed a head-to-head comparison of the ability of sera to recognize and neutralize SARS-CoV-2 variants of concern (VOCs; Alpha, Beta, Gamma, Delta and Omicron). Repeated serum sampling was performed 5 times during a year (from January 2021 till January 2022), including before and after booster vaccination with BNT162b2. FindingsFour weeks after completing the initial vaccination series, SARS-CoV-2 wild-type neutralizing antibody titers were highest in recipients of BNT162b2 and mRNA-1273 (geometric mean titers (GMT) of 197 [95% CI 149-260] and 313 [95% CI 218-448], respectively), and substantially lower in those vaccinated with the adenovirus vector-based vaccines AZD1222 and Ad26.COV2.S (GMT of 26 [95% CI 18-37] and 14 [95% CI 8-25] IU/ml, respectively). These findings were robust for adjustment to age and sex. VOCs neutralization was reduced in all vaccine groups, with the largest (9- to 80-fold) reduction in neutralization observed against the Omicron variant. The booster BNT162b2 vaccination increased neutralizing antibody titers for all groups with substantial improvement against the VOCs including the Omicron variant. Study limitations include the lack of cellular immunity data. ConclusionsOverall, this study shows that the mRNA vaccines appear superior to adenovirus vector-based vaccines in inducing neutralizing antibodies against VOCs four weeks after initial vaccination and after booster vaccination.

Ethnic disparities in incident SARS-CoV-2 infections became wider during the second wave of SARS-CoV-2 in Amsterdam, the Netherlands: a population-based longitudinal study (preprint)

Background Surveillance data in high-income countries have reported more frequent SARS-CoV-2 diagnoses in ethnic minority groups. We examined the cumulative incidence of SARS-CoV-2 and its determinants in six ethnic groups in Amsterdam, the Netherlands. Methods We analyzed participants enrolled in the population-based HELIUS cohort, who were tested for SARS-CoV-2-specific antibodies and answered COVID-19-related questions between June 24-October 9, 2020 (after the first wave) and November 23, 2020-March 31, 2021 (during the second wave). We modeled SARS-CoV-2 incidence from January 1, 2020-March 31, 2021 using Markov models adjusted for age and sex. We compared incidence between ethnic groups over time and identified determinants of incident infection within ethnic groups. Findings 2,497 participants were tested after the first wave; 2,083 (83·4%) were tested during the second wave. Median age at first visit was 54 years (interquartile range=44-61); 56·6% were female. Compared to Dutch-origin participants (15·9%), cumulative SARS-CoV-2 incidence was higher in participants of South-Asian Surinamese (25·0%; adjusted hazard ratio [aHR]=1·66;95%CI=1·16-2·40), African Surinamese (28·9%;aHR=1·97;95%CI=1·37-2·83), Turkish (37·0%;aHR=2·67;95%CI=1·89-3·78), Moroccan (41·9%;aHR=3·13;95%CI=2·22-4·42), and Ghanaian (64·6%;aHR=6·00;95%CI=4·33-8·30) origin. Compared to those of Dutch origin, differences in incidence became wider during the second versus first wave for all ethnic minority groups (all p for interaction<0.05), except Ghanaians. Having household members with suspected SARS-CoV-2 infection, larger household size, and low health literacy were common determinants of SARS-CoV-2 incidence across groups. Interpretation SARS-CoV-2 incidence was higher in the largest ethnic minority groups of Amsterdam, particularly during the second wave. Prevention measures, including vaccination, should be encouraged in these groups. Funding ZonMw, Public Health Service of Amsterdam, Dutch Heart Foundation, European Union, European Fund for the Integration of non-EU immigrants.

Cross-reactive antibodies after SARS-CoV-2 infection and vaccination (preprint)

Current SARS-CoV-2 vaccines are losing efficacy against emerging variants and may not protect against future novel coronavirus outbreaks, emphasizing the need for more broadly protective vaccines. To inform the development of a pan-coronavirus vaccine, we investigated the presence and specificity of cross-reactive antibodies against the spike (S) proteins of human coronaviruses (hCoV) after SARS-CoV-2 infection and vaccination. We found an 11 to 123-fold increase in antibodies binding to SARS-CoV and MERS-CoV as well as a 2 to 4-fold difference in antibodies binding to seasonal hCoVs in COVID-19 convalescent sera compared to pre-pandemic healthy donors, with the S2 subdomain of the S protein being the main target for cross-reactivity. In addition, we detected cross-reactive antibodies to all hCoV S proteins after SARS-CoV-2 S protein immunization in macaques, with higher responses for hCoV more closely related to SARS-CoV-2. These findings support the feasibility of and provide guidance for development of a pan-coronavirus vaccine.

Single-dose SARS-CoV-2 vaccine in a prospective cohort of COVID-19 patients (preprint)

Background The urgent need for, but limited availability of, SARS-CoV-2 vaccines worldwide has led to widespread consideration of dose sparing strategies, particularly single vaccine dosing of individuals with prior SARS-CoV-2 infection. Methods We evaluated SARS-CoV-2 specific antibody responses following a single-dose of BNT162b2 (Pfizer-BioNTech) mRNA vaccine in 155 previously SARS-CoV-2-infected individuals participating in a population-based prospective cohort study of COVID-19 patients. Participants varied widely in age, comorbidities, COVID-19 severity and time since infection, ranging from 1 to 15 months. Serum antibody titers were determined at time of vaccination and one week after vaccination. Responses were compared to those in SARS-CoV-2-naive health care workers after two BNT162b2 mRNA vaccine doses. Results Within one week of vaccination, IgG antibody levels to virus spike and RBD proteins increased 27 to 29-fold and neutralizing antibody titers increased 12-fold, exceeding titers of fully vaccinated SARS-CoV-2-naive controls (95% credible interval (CrI): 0.56 to 0.67 v. control 95% CrI: -0.16 to -0.02). Pre-vaccination neutralizing antibody titers had the largest positive mean effect size on titers following vaccination (95% CrI (0.16 to 0.45)). COVID-19 severity, the presence of comorbidities and the time interval between infection and vaccination had no discernible impact on vaccine response. Conclusion A single dose of BNT162b2 mRNA vaccine up to 15 months after SARS-CoV-2 infection provides neutralizing titers exceeding two vaccine doses in previously uninfected individuals. These findings support wide implementation of a single-dose mRNA vaccine strategy after prior SARS-CoV-2 infection.

Evolution of COVID-19 symptoms during the first 9 months after illness onset (preprint)

BackgroundFew longitudinal data on COVID-19 symptoms across the full spectrum of disease severity are available. We evaluated symptom onset, severity and recovery up to nine months after illness onset. MethodsThe RECoVERED Study is a prospective cohort study based in Amsterdam, the Netherlands. Participants aged>18 years were recruited following SARS-CoV-2 diagnosis via the local Public Health Service and from hospitals. Standardised symptom questionnaires were completed at recruitment, at one week and month after recruitment, and monthly thereafter. Clinical severity was defined according to WHO criteria. Kaplan-Meier methods were used to compare time from illness onset to symptom recovery, by clinical severity. We examined determinants of time to recovery using multivariable Cox proportional hazards models. ResultsBetween 11 May 2020 and 31 January 2021, 301 COVID-19 patients (167[55%] male) were recruited, of whom 99/301(32.9%) had mild, 140/301(46.5%) moderate, 30/301(10.0%) severe and 32/301(10.6%) critical disease. The proportion of symptomatic participants who reported at least one persistent symptom at 12 weeks after illness onset was greater in those with severe/critical disease (81.7%[95%CI=68.7-89.7%]) compared to those with mild or moderate disease (33.0%[95%CI=23.0-43.3%] and 63.8%[95%CI=54.8-71.5%]). Even at nine months after illness onset, almost half of all participants (42.1%[95%CI=35.6-48.5]) overall continued to report [≥]1 symptom. Recovery was slower in participants with BMI[≥]30kg/m2 (HR 0.51[95%CI=0.30-0.87]) compared to those with BMI<25kg/m2, after adjusting for age, sex and number of comorbidities. ConclusionsCOVID-19 symptoms persisted for nine months after illness onset, even in those with mild disease. Obesity was the most important determinant of speed of recovery from symptoms.

Hospitalisation rates differed by city district and ethnicity during the first wave of COVID-19 in Amsterdam, the Netherlands (preprint)

ABSTRACT Background It is important to gain insight into the burden of COVID-19 at city district level to develop targeted prevention strategies. We examined COVID-19 related hospitalisations by city district and migration background in the municipality of Amsterdam, the Netherlands. Methods We used surveillance data on all PCR-confirmed SARS-CoV-2 hospitalisations in Amsterdam until 31 May 2020, matched to municipal registration data on migration background. We calculated directly standardised (age, sex) rates (DSR) of hospitalisations, as a proxy of COVID-19 burden, per 100,000 population by city district and migration background. We calculated standardised rate differences (RD) and rate ratios (RR) to compare hospitalisations between city districts of varying socio-economic and health status and between migration backgrounds. We evaluated the effects of city district and migration background on hospitalisation after adjusting for age and sex using Poisson regression. Results Between 29 February and 31 May 2020, 2326 cases (median age 57 years [IQR=37-74]) were notified in Amsterdam, of which 596 (25.6%) hospitalisations and 287 (12.3%) deaths. 526/596 (88.2%) hospitalisations could be matched to the registration database. DSR were higher in individuals living in peripheral (South-East/New-West/North) city districts with lower economic and health status, compared to central districts (Centre/West/South/East) (RD=36.87,95%CI=25.79-47.96;RR=1.82,95%CI=1.65-1.99), and among individuals with a non-Western migration background compared to ethnic-Dutch individuals (RD=57.05,95%CI=43.34-70.75; RR=2.36,95%CI=2.17-2.54). City district and migration background were independently associated with hospitalisation. Conclusion City districts with lower economic and health status and those with a non-Western migration background had the highest burden of COVID-19 during the first wave of COVID-19 in Amsterdam.

SARS-CoV-2 antibody prevalence and determinants of six ethnic groups living in Amsterdam, the Netherlands: a population-based cross-sectional study, June-October 2020 (preprint)

Background Ethnic minorities have higher rates of SARS-CoV-2 diagnoses, but little is known about ethnic differences in past exposure. We aimed to determine whether prevalence and determinants of SARS-CoV-2 exposure varied between six ethnic groups in Amsterdam, the Netherlands. Methods Participants aged 25-79 years enrolled in a population-based prospective cohort were randomly selected within ethnic groups and invited to test for SARS-CoV-2-specific antibodies and answer COVID-19 related questions. We estimated prevalence and determinants of SARS-CoV-2 exposure within ethnic groups using survey-weighted logistic regression adjusting for age, sex and calendar time. Results Between June 24-October 9, 2020, we included 2497 participants. Adjusted SARS-CoV-2 seroprevalence was comparable between ethnic-Dutch (25/498; 5.5%, 95%CI=3.2-7.9), South-Asian Surinamese (22/451; 4.8%, 95%CI=2.1-7.5), African Surinamese (22/400; 8.2%, 95%CI=3.0-13.4), Turkish (30/408; 7.8%, 95%CI=4.3-11.2) and Moroccan (32/391; 7.0%, 95%CI=4.0-9.9) participants, but higher among Ghanaians (95/327; 26.5%, 95%CI=18.7-34.4). 57.1% of SARS-CoV-2-positive participants did not suspect or were unsure of being infected, which was lowest in African Surinamese (18.2%) and highest in Ghanaians (90.5%). Determinants of SARS-CoV-2 exposure varied across ethnic groups, while the most common determinant was having a household member suspected of infection. In Ghanaians, seropositivity was associated with older age, larger household sizes, living with small children, leaving home to work and attending religious services. Conclusions No remarkable differences in SARS-CoV-2 seroprevalence were observed between the largest ethnic groups in Amsterdam after the first wave of infections. The higher infection seroprevalence observed among Ghanaians, which passed mostly unnoticed, warrants wider prevention efforts and opportunities for non-symptom-based testing.

Human coronavirus reinfection dynamics: lessons for SARS-CoV-2 (preprint)

In the current COVID-19 pandemic a key unsolved question is the duration of acquired immunity in recovered individuals. The recent emergence of SARS-CoV-2 precludes a direct study on this virus, but the four seasonal human coronaviruses may reveal common characteristics applicable to all human coronaviruses. We monitored healthy subjects over a time span of 35 years (1985-2020), providing a total of 2473 follow up person-months, and determined a) the time to reinfection by the same seasonal coronavirus and b) the dynamics of coronavirus antibody depletion post-infection. An alarmingly short duration of protective immunity to coronaviruses was found. Reinfections occurred frequently at 12 months post-infection and there was for each virus a substantial reduction in antibody levels as soon as 6 months post-infection.