ABSTRACT
A cross-sectional SARS-CoV-2 serosurvey was conducted after the Omicron surge in Jamaica using 1,540 samples collected during March - May 2022 from persons attending antenatal, STI and non-communicable diseases clinics in Kingston, Jamaica. SARS-CoV-2 spike receptor binding domain (RBD) and/or nucleocapsid IgG antibodies were detected for 88.4% of the study population, with 77.0% showing evidence of previous SARS-CoV-2 infection. Of persons previously infected with SARS-CoV-2 and/or with COVID-19 vaccination, 9.6% were negative for spike RBD IgG, most of which were unvaccinated previously infected persons. Amongst unvaccinated previously infected people, age was associated with testing spike RBD IgG negative. When considering all samples, median spike RBD IgG levels were 131.6 BAU/mL for unvaccinated persons with serological evidence of past infection, 90.3 BAU/mL for vaccinated persons without serological evidence of past infection, and 896.1 BAU/mL for vaccinated persons with serological evidence of past infection. Our study of the first reported SARS-CoV-2 serosurvey in Jamaica shows extensive SARS-CoV-2 population immunity, identifies a substantial portion of the population lacking spike RBD IgG, and provides additional evidence for increasing COVID-19 vaccine coverage in Jamaica.
ABSTRACT
BackgroundSerological assays used to estimate SARS-CoV-2 seroprevalence rely on manufacturer cut-offs established based on more severe early cases who tended to be older. MethodsWe conducted a household-based serosurvey of 4,677 individuals from 2,619 households in Chennai, India from January to May, 2021. Samples were tested for SARS-CoV-2 IgG antibodies to the spike (S) and nucelocapsid (N) proteins. We calculated seroprevalence using manufacturer cut-offs and using a mixture model in which individuals were assigned a probability of being seropositive based on their measured IgG, accounting for heterogeneous antibody response across individuals. ResultsThe SARS-CoV-2 seroprevalence to anti-S and anti-N IgG was 62.0% (95% confidence interval [CI], 60.6 to 63.4) and 13.5% (95% CI, 12.6 to 14.5), respectively applying the manufacturers cut-offs, with low inter-assay agreement (Cohens kappa 0.15). With the mixture model, estimated anti-S IgG and anti-N IgG seroprevalence was 64.9% (95% Credible Interval [CrI], 63.8 to 66.0) and 51.5% (95% CrI, 50.2 to 52.9) respectively, with high inter-assay agreement (Cohens kappa 0.66). Age and socioeconomic factors showed inconsistent relationships with anti-S IgG and anti-N IgG seropositivity using manufacturers cut-offs, but the mixture model reconciled these differences. In the mixture model, age was not associated with seropositivity, and improved household ventilation was associated with lower seropositivity odds. ConclusionsWith global vaccine scale-up, the utility of the more stable anti-S IgG assay may be limited due to the inclusion of the S protein in several vaccines. SARS-CoV-2 seroprevalence estimates using alternative targets must consider heterogeneity in seroresponse to ensure seroprevalence is not underestimated and correlates not misinterpreted.
ABSTRACT
Globally, key subpopulations have a high risk of contracting SARS-CoV-2. In Uganda, limited access to personal protective equipment amidst lack of clarity on the extent of the community disease burden may exacerbate this situation. We assessed SARS-CoV-2 antibody seroprevalence among high-risk sub-populations, including healthcare workers, persons within the general population previously reporting experiencing key COVID-19 like symptoms and archived plasma specimens collected prior to confirmation of COVID-19 in Uganda. We collected venous blood from HCWs at selected health facilities and from population-cohort participants who reported specific COVID-19 like symptoms in a prior phone-based survey conducted during the first national lockdown (May-August 2020). Pre-lockdown plasma collected from individuals considered high risk for SARS-CoV-2 infection was retrieved. Specimens were tested for antibodies to SARS-CoV-2 using the CoronaChek rapid COVID-19 IgM/IgG lateral flow test assay. IgM only positive samples were confirmed using a chemiluminescent microparticle immunoassay (ARCHITECT AdviseDx SARS-CoV-2 IgM) which targets the spike. SARS-CoV-2 exposure was defined as either confirmed IgM, both IgM and IgG or sole IgG positivity. The seroprevalence of antibodies to SARS-CoV-2 in HCWs was 21.1% [95%CI: 18.2-24.2]. Of the phone-based survey participants, 11.9% [95%CI: 8.0-16.8] had antibodies to SARS-CoV-2. Among 636 pre-lockdown plasma specimens, 1.7% [95%CI: 0.9-3.1] were reactive. Findings suggest a high seroprevalence of antibodies to SARS-CoV-2 among HCWs and substantial exposure in persons presenting with specific COVID-19 like symptoms in the general population of South-central Uganda. Based on current limitations in serological test confirmation, it remains unclear whether pre-lockdown seropositivity implies prior SARS-CoV-2 exposure in Uganda.
ABSTRACT
While COVID-19 vaccines have been shown to significantly decrease morbidity and mortality, there is still much debate about optimal strategies of vaccine rollout. We tested identity-unlinked stored remnant blood specimens of patients at least 18 years presenting to the Johns Hopkins Hospital emergency department (ED) between May to November 2020 for IgG to SARS-CoV-2. Data on SARS-CoV-2 RT PCR were available for patients who were tested due to suspected infection. SARS-CoV-2 infections was defined as either a positive IgG and/or RT-PCR. SARS-CoV-2 infection clustering by zipcode was analyzed by spatial analysis using the Bernoulli model (SaTScan software, Version 9.7). Median age of the 7,461 unique patients visiting the ED was 47 years and 50.8% were female; overall, 740 (9.9%) unique patients had evidence of SARS-CoV-2 infection. Prevalence of infection in ED patients by ZIP code ranged from 4.1% to 22.3%. The observed number of cases in ZIP code C was nearly double the expected (observed/expected ratio = 1.99; 95% CI: 1.62, 2.42). These data suggest a targeted geospatial approach to COVID vaccination should be considered to maximize vaccine rollout efficiency and include high-risk populations that may otherwise be subjected to delays, or missed.
ABSTRACT
Serologic testing for SARS-CoV-2 antibodies can be used to confirm diagnosis, estimate seroprevalence, screen convalescent plasma donors, and assess vaccine efficacy. Several logistical and infrastructure challenges limit access to SARS-CoV-2 serologic testing. Dried blood spot (DBS) samples have been used for serology testing of various diseases in resource-limited settings. We examined the use of DBS samples and capillary blood (fingerstick) plasma collected in Microtainer tubes for SARS-CoV-2 testing with the automated Abbott ARCHITECT SARS-CoV-2 IgG (List 6R86) and IgM assays and use of venous whole blood with a prototype PANBIO rapid point-of-care lateral flow SARS-CoV-2 IgG assay. The ARCHITECT SARS-CoV-2 IgG assay was initially optimized for use with DBS, venous and capillary plasma, and venous whole blood collected from patients with symptoms and PCR-confirmed COVID-19 and negative asymptomatic controls. Assay linearity and reproducibility was confirmed with 3 contrived DBS samples, with sample stability and signal recovery after 14 days at room temperature. ARCHITECT SARS-CoV-2 IgG and IgM assay results showed high concordance between fingerstick DBS and venous DBS samples, and between fingerstick DBS and venous whole blood samples (n=61). Discordant results were seen in 3 participants (2 IgG, 1 IgM) who were in the process of seroreversion at the time of sample collection and had results near the assay cutoff. Use of fingerstick plasma collected in Microtainer tubes (n=109) showed 100% concordant results (R2=0.997) with matched patient venous plasma on the ARCHITECT SARS-CoV-2 IgG assay. High concordance of assay results (92.9% positive, 100% negative) was also observed for the PANBIO SARS-CoV-2 IgG assay compared to the ARCHITECT SARS-CoV-2 IgG assay run with matched venous plasma (n=61). Fingerstick DBS and plasma samples are easy and inexpensive to collect and, along with the use of rapid point-of-care testing platforms, will expand access to SARS-CoV-2 serology testing, particularly in resource-limited areas.
