Seroprevalence of SARS-CoV-2 antibodies and reduced risk of reinfection through 6 months: a Danish observational cohort study of 44 000 healthcare workers

ObjectivesAntibodies to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) are a key factor in protecting against coronavirus disease 2019 (COVID-19). We examined longitudinal changes in seroprevalence in healthcare workers (HCWs) in Copenhagen and the protective effect of antibodies against SARS-CoV-2.MethodsIn this prospective study, screening for antibodies against SARS-CoV-2 (ELISA) was offered to HCWs three times over 6 months. HCW characteristics were obtained by questionnaires. The study was registered at ClinicalTrials.gov, NCT04346186.ResultsFrom April to October 2020 we screened 44 698 HCWs, of whom 2811 were seropositive at least once. The seroprevalence increased from 4.0% (1501/37 452) to 7.4% (2022/27 457) during the period (p < 0.001) and was significantly higher than in non-HCWs. Frontline HCWs had a significantly increased risk of seropositivity compared to non-frontline HCWs, with risk ratios (RRs) at the three rounds of 1.49 (95%CI 1.34–1.65, p < 0.001), 1.52 (1.39–1.68, p < 0.001) and 1.50 (1.38–1.64, p < 0.001). The seroprevalence was 1.42- to 2.25-fold higher (p < 0.001) in HCWs from dedicated COVID-19 wards than in other frontline HCWs. Seropositive HCWs had an RR of 0.35 (0.15–0.85, p 0.012) of reinfection during the following 6 months, and 2115 out of 2248 (95%) of those who were seropositive during rounds one or two remained seropositive after 4–6 months. The 133 of 2248 participants (5.0%) who seroreverted were slightly older and reported fewer symptoms than other seropositive participants.ConclusionsHCWs remained at increased risk of infection with SARS-CoV-2 during the 6-month period. Seropositivity against SARS-CoV-2 persisted for at least 6 months in the vast majority of HCWs and was associated with a significantly lower risk of reinfection.     

Non-occupational and occupational factors associated with specific SARS-CoV-2 antibodies among hospital workers – A multicentre cross-sectional study

ObjectivesProtecting healthcare workers (HCWs) from coronavirus disease-19 (COVID-19) is critical to preserve the functioning of healthcare systems. We therefore assessed seroprevalence and identified risk factors for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) seropositivity in this population.MethodsBetween 22 June 22 and 15 August 2020, HCWs from institutions in northern/eastern Switzerland were screened for SARS-CoV-2 antibodies. We recorded baseline characteristics, non-occupational and occupational risk factors. We used pairwise tests of associations and multivariable logistic regression to identify factors associated with seropositivity.ResultsAmong 4664 HCWs from 23 healthcare facilities, 139 (3%) were seropositive. Non-occupational exposures independently associated with seropositivity were contact with a COVID-19-positive household (adjusted OR 59, 95% CI 33–106), stay in a COVID-19 hotspot (aOR 2.3, 95% CI 1.2–4.2) and male sex (aOR 1.9, 95% CI 1.1–3.1). Blood group 0 vs. non-0 (aOR 0.5, 95% CI 0.3–0.8), active smoking (aOR 0.4, 95% CI 0.2–0.7), living with children <12 years (aOR 0.3, 95% CI 0.2–0.6) and being a physician (aOR 0.2, 95% CI 0.1–0.5) were associated with decreased risk. Other occupational risk factors were close contact to COVID-19 patients (aOR 2.7, 95% CI 1.4–5.4), exposure to COVID-19-positive co-workers (aOR 1.9, 95% CI 1.1–2.9), poor knowledge of standard hygiene precautions (aOR 1.9, 95% CI 1.2–2.9) and frequent visits to the hospital canteen (aOR 2.3, 95% CI 1.4–3.8).DiscussionLiving with COVID-19-positive households showed the strongest association with SARS-CoV-2 seropositivity. We identified several potentially modifiable work-related risk factors, which might allow mitigation of the COVID-19 risk among HCWs. The lower risk among those living with children, even after correction for multiple confounders, is remarkable and merits further study.     

Seroprevalence of SARS-CoV-2 in blood donors from the Lodi Red Zone and adjacent Lodi metropolitan and suburban area

ObjectivesTo define the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in blood donors (referred to the first lockdown area (Lodi Red-Zone) of the Lombardy region and in a contiguous area that was not included in the first lockdown); to define the agreement between a commercial serological assay and a reference microneutralization assay; and to evaluate the persistence of SARS-CoV-2 neutralizing antibodies in a cohort of blood donors.MethodsBlood donors referred to the first lockdown area in Lombardy Region and the neighbouring area were analysed for SARS-CoV-2 IgG-specific antibodies during the period 18 March to 24 June 2020. Serum samples were analysed using both a chemiluminescent immunoassay (LIAISON® SARS-CoV-2 S1/S2 IgG, DiaSorin) for the quantitative characterization of SARS-CoV-2 anti-S1 and anti-S2 IgG antibodies and a neutralizing antibodies (NT-Abs) assay.ResultsIn the period from 18 March to 24 June, 1922 blood donors were tested for the presence of SARS-CoV-2 IgG showing a prevalence of 378/1922 (19.7%). A subgroup of 1139 blood donors were tested in parallel with a SARS-CoV-2 IgG assay and a microneutralization assay showing a prevalence of 22.2% and 21.6%, respectively. SARS-CoV-2 IgG quantification was correlated with NT-Abs titres. In 78.2% of participants the NT-Abs titre was maintained, but in 15.8% it decreased by one four-fold dilution and in 6.0% it increased by one four-fold dilution.ConclusionsThe duration of immunity of SARS-CoV-2 is crucial for the course of the pandemic and for this reason the monitoring of NT Abs is important. Despite a stable NT-Abs titre being observed in the majority of blood donors, our findings need to be validated in a long-term period of follow up.     

Seroprevalence and determinants of human herpes virus 8 infection in adult Nigerians with and without HIV-1 infection

Background

There is a dearth of studies on HHV8-HIV co-infections from Nigeria, even as both infections have been shown to be endemic in Africa. This study examined the seroprevalence and determinants of HHV8 infections in adult Nigerians with and without HIV-infection.

Methods

In 2007, a cross sectional study undertaken in a tertiary hospital in Zaria, northern Nigeria enrolled 71 HIV-1 positive adults without Kaposi''s sarcoma and 85 apparently healthy HIV-negative adult volunteers of the general population. Anti-lytic antibodies to HHV8 infection was determined by ELISA. A univariate analysis including age, sex, marital status, past sexually transmitted disease (STD), past blood transfusion, HIV/AIDS staging and CD4 count was used to determine variables associated with HHV8 seropositivity. Significant variables were adjusted in a logistic regression model expressed in odds ratio (OR) with 95% confidence interval (CI). P<0.05 was considered significant

Results

The seroprevalence of HHV8 infection was 62% in HIV-1 positive patients and 25.9% in HIV negative adults (p<0.001). A past history of STD [OR= 2.88, 95% CI= 1.0 – 8.2] and advanced HIV/AIDS (WHO stage 3 and 4) [OR=3.5, 95% CI= 1.21–10.1] were the only variables independently associated with HHV8 seropositivity in HIV-infected patients. In HIV-negative adults, none of the variables was significantly associated with HHV8 seropositivity.

Conclusion

The study findings suggest an adverse interaction between HHV8 and HIV-1. The higher prevalence of HHV8 infection in HIV-infected patients and its association with STD support a predominant sexual route of HHV8 transmission among adult Nigerians.     

Seroprevalences of Specific IgG Antibodies to Measles,Mumps, and Rubella in Korean Infants

In this study, the seroprevalences of measles, mumps, and rubella antibodies in infants were determined to assess the immunization strategy and control measures for these infectious diseases. Serum samples from infants < 1 year of age and their mothers were collected to measure the concentrations of specific IgG antibodies to measles, mumps, and rubella by enzyme-linked immunosorbent assay. For selected infant serum samples, measles-specific neutralizing antibody levels were determined by using the plaque reduction neutralization test. The sera from 295 of infants and 80 of their mothers were analyzed. No infants had past measles, mumps, or rubella infections. Almost all infants < 2 months of age were positive for measles and rubella IgG antibodies. However, seroprevalence of measles and rubella antibodies decreased with age, and measles IgG and rubella IgG were barely detectable after 4 months of age. The seroprevalence of mumps antibodies was lower than that of measles and rubella antibodies in infants ≤ 4 months old, and mumps IgG was barely detectable after 2 months of age. The seropositivity of measles-specific neutralizing antibody was 63.6% in infants aged 2 months and undetectable in infants ≥ 6 months old. Because the seropositivity rates of measles, mumps, and rubella antibodies were low after the first few months of age in Korean infants, active immunization with vaccines is strongly recommended for infants aged 6–11 months when measles is epidemic. Timely administration of the first dose of measles-mumps-rubella vaccine at 12 months of age should be encouraged in non-epidemic situations.     

Genetic characterization of porcine circovirus type 2 (PCV2) from pigs in high-seroprevalence areas in southeastern China

Increasing evidences indicate that porcine circovirus type 2 (PCV2) is the causative agent of the post-weaning multisystemic wasting syndrome (PMWS). In this study, the prevalence of PCV2 infection in swine herds in southeastern China was investigated by ELISA and PCR, as well as the genetic characteristics by nucleic acid sequencing. Seroprevalence of PCV2 in samples collected from 89 swine herds was significantly higher by ELISA in post-weaning (54.1%) and growing piglets (49.9%) than that of suckling pigs (33.3%) with an average rate of 46.0% (819/1779). Seventy-eight cases out of 159 diseased pigs from these herds were PCV2 positive by PCR. Furthermore, the PCV2-positve rate at herds level in 2005 and 2006 were much higher than that in 2004 (65.63% or 69.23% vs. 32.26%, respectively), indicating that PCV-2 infection expanded rapidly over the past two years. To provide new insights into the extent of genetic heterogeneity of PCV2 isolates in southeastern China, the ORF2 genes of 27 isolates from the area during January 2004–March 2007 were sequenced and aligned. While closely related to each other with identity of 98.0–100%, these isolates displayed lower homologies to those from other regions of China (90.6–100%) or to some foreign isolates (91.3–98.9%). Alignment of deduced amino acid sequences of capsid protein identified two major hyper-variable regions (positions 53–91 and 185–215) in isolates obtained in this study, which were within or close to the putative epitope domains. The substitutions consequently resulted in higher hydrophilicity of the epitope region (positions 47–85). Phylogenetic analysis revealed two clusters of 48 isolates including those from Genbank: the large cluster I consisting of two subgroups and cluster II containing most of foreign isolates owing to the residue substitutions in epitope domains (amino acid positions 80, 86, 88 and 91). While the subgroup Ib contained all the isolates with ORF2 of 705 bp in length, the 27 isolates we sequenced were clustered exclusively in subgroup Ia together with some other Chinese strains. We conclude that PCV2 isolates prevailing in southeastern China were genetically different from those of other countries.     

A review of testing used in seroprevalence studies on measles and rubella

Seroprevalence studies are an essential tool to monitor the efficacy of vaccination programmes, to understand population immunity and to identify populations at higher risk of infection. An overarching review of all aspects of seroprevalence studies for measles and rubella published between 1998 and June 2014 was undertaken and the findings reported elsewhere. This paper details the considerable variation in the testing formats identified in the review. Apart from serum/plasma samples, testing of oral fluid, breast milk, dry blood spots and capillary whole blood were reported. Numerous different commercial assays were employed, including microtitre plate assays, automated immunoassays and classical haemagglutination inhibition and neutralisation assays. A total of 29 of the 68 (43%) measles and 14 of the 58 (24%) rubella studies reported qualitative test results. Very little information on the testing environment, including quality assurance mechanisms used, was provided. Due to the large numbers of testing systems, the diversity of sample types used and the difficulties in accurate quantification of antibody levels, the results reported in individual studies were not necessarily comparable. Further efforts to standardise seroprevalence studies may overcome this deficiency.     

Seroprevalence of dengue in Trinidad using rapid test kits: a cord blood survey

A cross-sectional sero-epidemiological study was conducted to determine the prevalence of dengue in Trinidad. Two commercial rapid test kits, PanBio Dengue Duo IgM and IgG Rapid Strip Test and the Bio-Check Plus Dengue G/M Cassette Test (Brittney) were used. The immunosorbent assay (ELISA) (FOCUS Technologies, California) was used as the control. One hundred and twenty five cord blood samples were collected (46 from Mt. Hope Women's Hospital (MH) and 79 from the San Fernando General Hospital (SF)). All blood samples were tested in accordance with the two rapid kits and ELISA assay manufacturer's instructions. From 125 cord blood samples, the IgG FOCUS ELISA results showed 93.5 and 95% infections at MH and SF, respectively. Whereas the Brittney and PanBio kits showed 10.9 and 5.1%, and 26.1 and 50.6% for MH and SF, respectively. Based on the FOCUS ELISA (control) assays, the combined seroprevalence rate from north and south Trinidad was 94.4%. IgG and IgM sensitivity and specificity levels were higher in the PanBio than Brittney test kits. The high seroprevalence rates observed in Trinidad are discussed to stimulate more research to explain this phenomenon and to prevent the Southeast Asian scenario from developing in the Americas.     

Helicobacter pylori serology in a birth cohort of New Zealanders from age to 26

AIM: To determine seroprevalence of Helicobacter pylori(H pylori) in the Dunedin Multidisciplinary Health and Development Study (DMHDS) at age 26 in order toinvestigate seroconversion and seroreversion from age 11 to 26 and the association of seropositivity with risk factors for H pylori infection. METHODS: Participants in the DMHDS at age 26 and retrospectively at age 21 were tested for H pylori antibodies using two commercially available ELISA kits. Gender, socioeconomic status (SES), smoking, educational attainment and employment at age 26 were tested for association with H pylori seropositivity.RESULTS: At ages 21 and 26, seroprevalence of H pylori using one or other kit was 4.2% (n = 795) and 6.3% (n = 871) respectively. Seroreversion rate was lower than serocon version rate (0.11% vs0.53% per person-year) in contrast to the period from age 11 to 21 when seroreversion rate exceeded seroconversion rate (0.35% vs 0.11% per person-year). Serology in those tested at ages 11, 21, and 26 remained unchanged in 93.6% of the sample. Seroprevalence at age 26 was lower among those with a secondary school qualification (P = 0.042) but was not associated with gender, SES, smoking or employment status. CONCLUSION: H pylori seroprevalence in a New Zealandbirth cohort remains low between ages 11 and 26. H pylori infection remains stable from childhood to adulthood although seroreversion seems to be more common in the adolescent years than in young adults.