High SARS-CoV-2 Prevalence among Healthcare Workers in Cochabamba, Bolivia.

Healthcare workers (HCWs) are at increased risk of SARS-CoV-2 infection. The aim of the study was to estimate the SARS-CoV-2 seroprevalence among HCWs in Cochabamba, Bolivia and to determine the potential risk factors. In January 2021, a cross-sectional SARS-CoV-2 seroprevalence study was conducted in 783 volunteer clinical and non-clinical HCWs in tertiary care facilities. It was based on IgG detection using ELISA, chemiluminiscence, and seroneutralisation tests from dried blood spots. Analysis revealed a high seroprevalence (43.4%) of SARS-CoV-2 IgG antibodies. The combination of anosmia and ageusia (OR: 68.11; 95%-CI 24.83-186.80) was predictive of seropositivity. Belonging to the cleaning staff (OR: 1.94; 95%-CI 1.09-3.45), having more than two children in the same house (OR: 1.74; 95%-CI 1.12-2.71), and having been in contact with a close relative with COVID-19 (OR: 3.53; 95%-CI 2.24-5.58) were identified as risk factors for seropositivity in a multivariate analysis. A total of 47.5% of participants had received medication for COVID-19 treatment or prevention, and only ~50% of symptomatic subjects accessed PCR or antigenic testing. This study confirms a massive SARS-CoV-2 attack rate among HCWs in Cochabamba by the end of January 2021. The main risk factors identified are having a low-skilled job, living with children, and having been in contact with an infected relative in the household.

SARS-CoV-2 IgG seroprevalence surveys in blood donors before the vaccination campaign, France 2020-2021.

We conducted a cross-sectional study for SARS-CoV-2 anti-S1 IgG prevalence in French blood donors (n = 32605), from March-2020 to January-2021. A mathematical model combined seroprevalence with a daily number of hospital admissions to estimate the probability of hospitalization upon infection and determine the number of infections while correcting for antibody decay. There was an overall seroprevalence increase over the study period and we estimate that ∼15% of the French population had been infected by SARS-CoV-2 by January-2021. The infection/hospitalization ratio increased with age, from 0.31% (18-30yo) to 4.5% (61-70yo). Half of the IgG-S1 positive individuals had no detectable antibodies 4 to 5 months after infection. The seroprevalence in group O donors (7.43%) was lower (p = 0.003) than in A, B, and AB donors (8.90%). We conclude, based on seroprevalence data and mathematical modeling, that a large proportion of the French population was unprotected against severe disease prior to the vaccination campaign.

Long-lasting Symptoms After an Acute COVID-19 Infection and Factors Associated With Their Resolution.

Importance: Persistent symptoms after SARS-CoV-2 infection are an emerging public health problem. The duration of these symptoms remains poorly documented. Objective: To describe the temporal dynamics of persistent symptoms after SARS-CoV-2 infection and the factors associated with their resolution. Design, Setting, and Participants: This cross-sectional study involved 53 047 participants from 3 French adult population-based cohorts (CONSTANCES [Consultants des Centres d'Examens de Santé], E3N/E4N, and Nutrinet-Santé) who were included in a nationwide survey about SARS-CoV-2 infection. All participants were asked to complete self-administered questionnaires between April 1 and June 30, 2020. Variables included sociodemographic characteristics, comorbid conditions, COVID-19 diagnosis, and acute symptoms. Blood samples were obtained for serologic analysis between May 1 and November 30, 2020, from patients with SARS-CoV-2 infection defined as enzyme-linked immunosorbent assay immunoglobulin G antispike detection confirmed with a neutralization assay. A follow-up internet questionnaire was completed between June 1 and September 30, 2021, with details on persistent symptoms, their duration, and SARS-CoV-2 infection diagnosis by polymerase chain reaction. Main Outcomes and Measures: Persistent symptoms were defined as symptoms occurring during the acute infection and lasting 2 or more months. Survival models for interval-censored data were used to estimate symptom duration from the acute episode. Multivariable adjusted hazard ratios (HRs) were estimated for age, sex, and comorbid conditions. Factors associated with the resolution of symptoms were assessed. Results: A total of 3972 participants (2531 women [63.7%; 95% CI, 62.2%-65.2%]; mean [SD] age, 50.9 [12.7] years) had been infected with SARS-CoV-2. Of these 3972 participants, 2647 (66.6% [95% CI, 65.1%-68.1%]) reported at least 1 symptom during the acute phase. Of these 2647 participants, 861 (32.5% [95% CI, 30.8%-34.3%]) reported at least 1 persistent symptom lasting 2 or more months after the acute phase. After 1 year of follow-up, the estimated proportion of individuals with complete symptom resolution was 89.9% (95% CI, 88.7%-90.9%) with acute symptoms. Older age (>60 years; HR, 0.78; 95% CI, 0.68-0.90), female sex (HR, 0.64; 95% CI, 0.58-0.70), history of cancer (HR, 0.61; 95% CI, 0.47-0.79), history of tobacco consumption (HR, 0.80; 95% CI, 0.73-0.88), high body mass index (≥30: HR, 0.75; 95% CI, 0.63-0.89), and high number of symptoms during the acute phase (>4; HR, 0.43; 95% CI, 0.39-0.48) were associated with a slower resolution of symptoms. Conclusions and Relevance: In this cross-sectional study, persistent symptoms were still present in 10.1% of infected individuals at 1 year after SARS-CoV-2 infection. Given the high level of cumulative incidence of COVID-19, the absolute prevalent number of people with persistent symptoms is a public health concern.

A Cross-Sectional Study of Exposure Factors Associated with Seropositivity for SARS-CoV-2 Antibodies during the Second Epidemic Wave among a Sample of the University of Corsica (France).

This study aimed to estimate the seroprevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection within the staff and student populations of the University of Corsica (France) during the second wave of the epidemic. METHODS: A cross-sectional survey was conducted from 23 November 2020 to 31 January 2021. The participants underwent blood sampling using a fingerstick procedure and completed an anonymized questionnaire. Sera were tested for the presence of anti-SARS-CoV-2 IgG (ELISA-S) and, if positive, with an in-house virus neutralization test (VNT). RESULTS: A total of 418 persons were included in the study. The overall seroprevalence was 12.8% (95% confidence interval (CI), 9.8-16.6%). A total of 15 (31%) of the 49 individuals who had a positive ELISA-S also had a positive VNT. Seropositivity was associated with living at the city campus during the week and on weekends (OR = 3.74 [1.40-12.00]), using public transportation/carpooling (OR = 2.00 [1.01-4.02]), and being in contact with a person who tested positive for SARS-CoV-2 (OR = 2.32 [1.20-4.40]). The main symptoms associated with seropositivity were "having had an acute respiratory infection" (OR = 3.05 [1.43-6.43]) and "experiencing loss of smell" (OR = 16.4 [5.87-50.7]). CONCLUSION: These results could be useful for SARS-CoV-2 prevention and control on university campuses.

Determining the best window for BNT162b2 mRNA vaccination for SARS-CoV-2 in patients with multiple sclerosis receiving anti-CD20 therapy.

We studied the serologic response to the BNT162b2 mRNA vaccine at four weeks after the second dose in patients with RRMS treated with rituximab with extended-interval dosing (n = 26). At four weeks, 73% of patients were seropositive. No patient without B cells at the first dose (n = 4) was seropositive. Four of seven (57%) patients with B-cell proportion >0% and ≤5% were seropositive. All patients with B-cell proportion >5% (n = 15) were seropositive. In all patients, quantitative ELISA measures after vaccination were correlated with B-cell counts measured before vaccination. In patients receiving rituximab, seropositivity after BNT162b2 mRNA vaccination emerged only after B-cell repopulation.

Age, COVID-19-like symptoms and SARS-CoV-2 seropositivity profiles after the first wave of the pandemic in France.

BACKGROUND: The interplay between age and symptoms intensity on antibody response to SARS-CoV-2 infection has not been studied in a general population setting. METHODS: We explored the serologic profile of anti-SARS-CoV-2 antibodies after the first wave of the pandemic, by assessing IgG against the spike protein (ELISA-S), IgG against the nucleocapsid protein (ELISA-NP) and neutralizing antibodies (SN) in 82,126 adults from a French population-based multi-cohort study. RESULTS: ELISA-S positivity was increased in 30- to 49-year-old adults (8.5%) compared to other age groups (5.6% in 20- to 29-year-olds, 2.8% in ≥ 50-year-olds). In the 3681 ELISA-S positive participants, ELISA-NP and SN positivity exhibited a U-shaped relationship with age, with a lower rate in 30- to 49-year-old adults, and was strongly associated with COVID-19-like symptoms. CONCLUSION: Our study confirms the independent role of age and symptoms on the serologic profile of anti-SARS-CoV-2 antibodies, but the non-linear relationship with age deserves further investigation.

Impact of the Second Epidemic Wave of SARS-CoV-2: Increased Exposure of Young People.

We aimed to use serological surveillance based on serial cross-sectional sampling of residual sera obtained from clinical laboratories to compare the differences in age and sex profiles of infected persons in the first and second waves of SARS-CoV-2 in Corsica, France. Residual sera were obtained, including samples from individuals of all ages collected for routine screening or clinical management by clinical laboratories. All the sera collected were tested for the presence of anti-SARS-CoV-2 IgG using a kit for semi-quantitative detection of IgG antibodies against the S1 domain of the viral spike protein (ELISA-S). Samples that were borderline and positive in ELISA-S were tested with an in-house virus neutralization test. During the second-wave period, we collected between 6 November, 2020 and 12 February, 2021, 4,505 sera from patients aged 0-101 years (60.4% women). The overall weighted seroprevalence of residual sera collected during the second-wave period [8.04% (7.87-9.61)] was significantly higher than the overall weighted seroprevalence estimated at the end of the first wave between 16 April and 15 June, 2020 [5.46% (4.37-7.00)] (p-value = 0.00025). Ninety-eight (30.1%) of the 326 samples tested in the VNT assay had a positive neutralization antibody titer. Estimated seroprevalence increased significantly for men [odds ratio (OR) OR = 1.80 (1.30-2.54); p-value = 0.00026] and for people under 30 years of age [OR = 2.17 (1.46-3.28); p-value = 0.000032]. This increase was observed in young adults aged 20-29 years among whom antibody frequencies were around four-fold higher than those observed at the end of the first wave. In conclusion, our seroprevalence estimates, including the proportion of the participants who had produced neutralizing antibodies, indicate that in February, 2021 the population of Corsica was still far from being protected against SARS-Cov-2 by "herd immunity."

Antibody status and cumulative incidence of SARS-CoV-2 infection among adults in three regions of France following the first lockdown and associated risk factors: a multicohort study.

BACKGROUND: We aimed to estimate the seropositivity to anti-SARS-CoV-2 antibodies in May-June 2020 after the first lockdown period in adults living in three regions in France and to identify the associated risk factors. METHODS: Between 4 May 2020 and 23 June 2020, 16 000 participants in a survey on COVID-19 from an existing consortium of three general adult population cohorts living in the Ile-de-France (IDF) or Grand Est (GE) (two regions with high rate of COVID-19) or in the Nouvelle-Aquitaine (NA) (with a low rate) were randomly selected to take a dried-blood spot for anti-SARS-CoV-2 antibodies assessment with three different serological methods (ClinicalTrial Identifier #NCT04392388). The primary outcome was a positive anti-SARS-CoV-2 ELISA IgG result against the spike protein of the virus (ELISA-S). Estimates were adjusted using sampling weights and post-stratification methods. Multiple imputation was used to infer the cumulative incidence of SARS-CoV-2 infection with adjustments for imperfect tests accuracies. RESULTS: The analysis included 14 628 participants, 983 with a positive ELISA-S. The weighted estimates of seropositivity and cumulative incidence were 10.0% [95% confidence interval (CI): 9.1%, 10.9%] and 11.4% (95% CI: 10.1%, 12.8%) in IDF, 9.0% (95% CI: 7.7%, 10.2%) and 9.8% (95% CI: 8.1%, 11.8%) in GE and 3.1% (95% CI: 2.4%, 3.7%) and 2.9% (95% CI: 2.1%, 3.8%) in NA, respectively. Seropositivity was higher in younger participants [odds ratio (OR) = 1.84 (95% CI: 1.79, 6.09) in <40 vs 50-60 years old and OR = 0.56 (95% CI: 0.42, 0.74) in ≥70 vs 50-60 years old)] and when at least one child or adolescent lived in the same household [OR = 1.30 (95% CI: 1.11, 1.53)] and was lower in smokers compared with non-smokers [OR = 0.71 (95% CI: 0.57, 0.89)]. CONCLUSIONS: Seropositivity to anti-SARS-CoV-2 antibodies in the French adult population was ≤10% after the first wave. Modifiable and non-modifiable risk factors were identified.