Using sero-epidemiology to monitor disparities in vaccination and infection with SARS-CoV-2

Pediatric humoral immune responses and infection risk after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and two-dose vaccination during SARS-CoV-2 omicron BA.5 and BN.1 variants predominance in South Korea

Background

Humoral immune responses and infection risk after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and coronavirus disease 2019 (COVID-19) vaccination during the Omicron BA.5 and BN.1 variants predominant period remains unexplored in pediatric population.

Methods

We examined anti-spike (anti-S) immunoglobulin G (IgG) responses in a total of 986 children aged 4-18 years who visited outpatient clinics between June 2022 and January 2023, with a history of SARS-CoV-2 infection alone, completed two doses of COVID-19 vaccination alone, vaccine-breakthrough infection (i.e., infection after the single dose of vaccination), and no antigenic exposure. Furthermore, to determine SARS-CoV-2 infection risk, the incidence of newly developed SARS-CoV-2 infection was investigated up to March 2023.

Results

The anti-S IgG levels in the 'vaccine-breakthrough infection' group exceeded those in the 'infection alone' and 'vaccination alone' groups (both P <0.01). Furthermore, the 'vaccination alone' group experienced more rapid anti-S IgG waning than the 'infection alone' and 'vaccine-breakthrough infection' groups (both P <0.01). We could not identify newly developed SARS-CoV-2 infection in the 'vaccine-breakthrough infection' group.

Conclusion

Our findings suggest that hybrid immunity, acquired from SARS-CoV-2 infection and COVID-19 vaccination, was a potentially higher and longer-lasting humoral immune response and protected against SARS-CoV-2 infection in pediatric population during Omicron BA.5 and BN.1 variants predominant.

Early Pandemic Access to COVID-19 Testing in the Somali Community in King County, Washington, USA: a Mixed-Methods Evaluation

BACKGROUND

Racial and ethnic disparities in COVID-19 infection and outcomes have been documented, but few studies have examined disparities in access to testing.

METHODS

We conducted a mixed methods study of access to COVID-19 testing in the Somali immigrant community in King County, Washington, USA, early during the COVID-19 pandemic. In September 2020-February 2021, we conducted quantitative surveys in a convenience sample (n = 528) of individuals who had accessed PCR testing, recruited at King County testing sites near Somali population centers and through social media outreach in the Somali community. We compared self-identified Somali and non-Somali responses using Chi-square and Wilcoxon rank sum tests. We also conducted three Somali-language focus groups (n = 26) by video conference to explore Somali experiences with COVID-19 testing, and in-depth interviews with King County-based policymakers and healthcare workers (n = 13) recruited through the research team's professional network to represent key demographics and roles. Data were analyzed using qualitative rapid analysis to explore the county's COVID-19 testing landscape.

RESULTS

Among 420 survey respondents who had received COVID-19 testing in the prior 90 days, 29% of 140 Somali vs. 11% of 280 non-Somali respondents tested because of symptoms (p = 0.001), with a trend for longer time from symptom onset to testing (a measure of testing access) among Somali respondents (median 3.0 vs. 2.0 days, p = 0.06). Focus groups revealed barriers to testing, including distrust, misinformation, stigma, language, lack of awareness, and transportation. Stakeholders responding from all sectors highlighted the importance of community partnership to improve access.

CONCLUSION

Somali communities experience barriers to COVID-19 testing, as evidenced by the longer time from symptom onset to testing and corroborated by our qualitative findings. These barriers, both structural and community-derived, may be overcome through partnerships between government and community to support community-led, multilingual service delivery and racial representation among medical staff.

Accounting for assay performance when estimating the temporal dynamics in SARS-CoV-2 seroprevalence in the U.S

Reconstructing the incidence of SARS-CoV-2 infection is central to understanding the state of the pandemic. Seroprevalence studies are often used to assess cumulative infections as they can identify asymptomatic infection. Since July 2020, commercial laboratories have conducted nationwide serosurveys for the U.S. CDC. They employed three assays, with different sensitivities and specificities, potentially introducing biases in seroprevalence estimates. Using models, we show that accounting for assays explains some of the observed state-to-state variation in seroprevalence, and when integrating case and death surveillance data, we show that when using the Abbott assay, estimates of proportions infected can differ substantially from seroprevalence estimates. We also found that states with higher proportions infected (before or after vaccination) had lower vaccination coverages, a pattern corroborated using a separate dataset. Finally, to understand vaccination rates relative to the increase in cases, we estimated the proportions of the population that received a vaccine prior to infection.

Performance of Dried Blood Spot Samples in SARS-CoV-2 Serolomics

Numerous sero-epidemiological studies have been initiated to investigate the spread and dynamics of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To address the concomitant need for serological high-throughput assays, a bead-based multiplex serology assay, specific for SARS-CoV-2, had been developed. SARS-CoV-2 serolomics allows for measuring antibody responses to almost the entire SARS-CoV-2 proteome in up to 2000 serum samples per day. To enlarge the pool of eligible sample collection methods, we here test the compatibility of serolomics with dried blood spot (DBS)-derived eluates. Antibody levels of nine SARS-CoV-2 antigens, including the nucleocapsid (N) and receptor-binding domain of the spike protein (S1-RBD), were measured in 142 paired DBS and serum samples. The numeric correlation between the two sample types was high, with a Pearson’s r of 0.88 for both S1-RBD and N and intraclass correlation coefficients of 0.93 and 0.92, respectively. Systematically reduced antibody levels in DBS eluates were compensated by lowering the cutoffs for seropositivity accordingly. This enabled the concordant classification of SARS-CoV-2 seropositivity, without loss in sensitivity. Antibody levels against accessory SARS-CoV-2 antigens also showed a high concordance, demonstrating that DBS-derived eluates are eligible for SARS-CoV-2 serolomics. DBS cards facilitate the collection of blood samples, as they obviate the need for medically trained personnel and can be shipped at room temperature. In combination with SARS-CoV-2 serolomics, DBS cards enable powerful sero-epidemiological studies, thus allowing for the monitoring of patients and epidemiological analyses in resource-poor settings.