Seroprevalence of SARS-CoV-2 infection and associated factors among Bangladeshi slum and non-slum dwellers in pre-COVID-19 vaccination era: October 2020 to February 2021

A handheld luminometer with sub-attomole limit of detection for distributed applications in global health

Luminescence is ubiquitous in biology research and medicine. Conceptually simple, the detection of luminescence nonetheless faces technical challenges because relevant signals can exhibit exceptionally low radiant power densities. Although low light detection is well-established in centralized laboratory settings, the cost, size, and environmental requirements of high-performance benchtop luminometers are not compatible with geographically-distributed global health studies or resource-constrained settings. Here we present the design and application of a ~$700 US handheld, battery-powered luminometer with performance on par with high-end benchtop instruments. By pairing robust and inexpensive Silicon Photomultiplier (SiPM) sensors with a low-profile shutter system, our design compensates for sensor non-idealities and thermal drift, achieving a limit of detection of 1.6E-19 moles of firefly luciferase. Using these devices, we performed two pilot cross-sectional serology studies to assess sars-cov-2 antibody levels: a cohort in the United States, as well as a field study in Bangladesh. Results from both studies were consistent with previous work and demonstrate the device's suitability for distributed applications in global health.

Serosurveillance among urban slum and non-slum populations immunized with COVID-19 vaccines in Bangladesh

Using two rounds of serosurveillance, we aimed to observe the COVID-19 vaccination status and the dynamics of antibody responses to different vaccines among urban slum and non-slum populations of Bangladesh. Adults (>18 years) and children (10-17 years) were enrolled in March and October 2022. Data including COVID-19 vaccine types and dosage uptake were collected. SARS-CoV-2 spike (S)-specific antibodies were measured in blood. The proportion of vaccinated children was significantly lower among slum than non-slum populations. Two doses of vaccines showed an increase in the level of anti-S-antibodies up to 2 months, followed by reduced levels at 2-6 months and a resurgence at 6-12 months. Children showed significantly higher anti-S-antibodies after two doses of the Pfizer-BioNTech vaccine than adults; however, after 6 months, the level of antibodies declined in younger children (10 - < 12 years). In a mixed vaccine approach, mRNA vaccines contributed to the highest antibody response whether given as the first two doses or as the third dose. Our findings emphasized the need for increasing the coverage of COVID-19 vaccination among slum children and booster dosing among all children. The use of mRNA vaccines in the mixed vaccination approach was found to be useful in boosting the antibody response to SARS-CoV-2.

Factors Associated with Reported COVID-like Symptoms and Seroprevalence Data Matched with COVID-like Symptoms in Slums and Non-Slums of Two Major Cities in Bangladesh

OBJECTIVES

To examine the levels and socio-demographic differentials of: (a) reported COVID-like symptoms; and (b) seroprevalence data matched with COVID-like symptoms.

METHODS

Survey data of reported COVID-like symptoms and seroprevalence were assessed by Roche Elecsys^® Anti-SARS-CoV-2 immunoassay. Survey data of 10,050 individuals for COVID-like symptoms and seroprevalence data of 3205 individuals matched with COVID-like symptoms were analyzed using bivariate and multivariate logistic analysis.

RESULTS

The odds of COVID-like symptoms were significantly higher for Chattogram city, for non-slum, people having longer years of schooling, working class, income-affected households, while for households with higher income had lower odd. The odds of matched seroprevalence and COVID-like symptoms were higher for non-slum, people having longer years of schooling, and for working class. Out of the seropositive cases, 37.77% were symptomatic-seropositive, and 62.23% were asymptomatic, while out of seronegative cases, 68.96% had no COVID-like symptoms.

CONCLUSIONS

Collecting community-based seroprevalence data is important to assess the extent of exposure and to initiate mitigation and awareness programs to reduce COVID-19 burden.

Evaluating the seroprevalence of SARS-CoV-2 IgG in five different districts of Bangladesh. A seroepidemiological study

BACKGROUND

We aimed to measure the seroprevalences and levels of anti-SARS-CoV-2 IgG in children, unvaccinated and vaccinated adults in five districts of Bangladesh and thus, investigate the association of seroprevalence and anti-SARS-CoV-2 IgG level with respect to different attributes of study participants.

METHODS

In the present study, the seroprevalences and levels of plasma anti-SARS-CoV-2 IgG were measured in children (n = 202), unvaccinated adults (n = 112), and vaccinated adults (n = 439) using quantitative ELISA.

RESULTS

The overall seroprevalence in the three groups of the study participants were 58.3% (90%CrI: 52.3-64.2%), 62.2% (90%CrI: 54.4-70.0%) and 90.7% (90%CrI: 88.3-92.9%), respectively. Multivariate logistic and linear regression revealed no significant association of seropositivity and levels of anti-SARS-CoV-2 IgG with the baseline characteristics of the children. AB blood group (vs A; aOR=0.21, 95% CI: 0.04-0.92, p = 0.04), O blood group (vs A; aOR=0.09, 95% CI: 0.02-0.32, p = 0.0004), BMI (aOR=1.61, 95% CI: 1.14-2.37, p = 0.01) and overweight obesity status (vs normal, aOR=0.12, 95% CI: 0.02-0.76, p = 0.03) were significantly associated with seropositivity in unvaccinated adults after adjusting for confounders. Age (p = 0.002) was significantly associated with anti-SARS-CoV-2 level in vaccinated adults after adjusting for confounders. Most of the children and unvaccinated adults belonged to the lower antibody response class which implicates the necessity of vaccination.

CONCLUSION

This study portrays a better way of evaluating transmission of virus and gain a better understanding of the true extent of infection as illustrated by the high rates of seroprevalences in children and unvaccinated adults. The findings of this study depicted from the antibody response also suggest the importance of vaccination.

Immune cell landscape in symptomatic and asymptomatic SARS-CoV-2 infected adults and children in urban Dhaka, Bangladesh

OBJECTIVES

The study of cellular immunity to SARS-CoV-2 is crucial for evaluating the course of the COVID-19 disease and for improving vaccine development. We aimed to assess the phenotypic landscape of circulating lymphocytes and mononuclear cells in adults and children who were seropositive to SARS-CoV-2 in the past 6 months.

METHODS

Blood samples (n = 350) were collected in a cross-sectional study in Dhaka, Bangladesh (Oct 2020-Feb 2021). Plasma antibody responses to SARS-CoV-2 were determined by an electrochemiluminescence immunoassay while lymphocyte and monocyte responses were assessed using flow cytometry including dimensionality reduction and clustering algorithms.

RESULTS

SARS-CoV-2 seropositivity was observed in 52% of adults (18-65 years) and 56% of children (10-17 years). Seropositivity was associated with reduced CD3+T cells in both adults (beta(β) = -2.86; 95% Confidence Interval (CI) = -5.98, 0.27) and children (β = -8.78; 95% CI = -13.8, -3.78). The frequencies of T helper effector (CD4+TEFF) and effector memory cells (CD4+TEM) were increased in seropositive compared to seronegative children. In adults, seropositivity was associated with an elevated proportion of cytotoxic T central memory cells (CD8+TCM). Overall, diverse manifestations of immune cell dysregulations were more prominent in seropositive children compared to adults, who previously had COVID-like symptoms. These changes involved reduced frequencies of CD4+TEFF cells and CD163+CD64+ classical monocytes, but increased levels of intermediate or non-classical monocytes, as well as CD8+TEM cells in symptomatic children.

CONCLUSION

Seropositive individuals in convalescence showed increased central and effector memory T cell phenotypes and pro-resolving/healing monocyte phenotypes compared to seronegative subjects. However, seropositive children with a previous history of COVID-like symptoms, displayed an ongoing innate inflammatory trait.

Antibody response to different COVID-19 vaccines among the migrant workers of Bangladesh

Background

Due to the ongoing COVID-19 pandemic, various host countries such as Singapore, imposed entry requirements for migrant workers including pre-departure COVID-19 seroconversion proof. To combat COVID-19 worldwide, several vaccines have acquired conditional approval. This study sought to assess antibody levels after immunization with different COVID-19 vaccines among the migrant workers of Bangladesh.

Methods

Venous blood samples were collected from migrant workers who were vaccinated with different COVID-19 vaccines (n=675). Antibodies to SARS-CoV-2 spike protein (S) and nucleocapsid protein (N) were determined using Roche Elecsys^® Anti-SARS-CoV-2 S and N immunoassay, respectively.

Results

All participants receiving COVID-19 vaccines showed antibodies to S-protein, while 91.36% were positive for N-specific antibodies. The highest anti-S antibody titers were found among the workers who completed booster doses (13327 U/mL), received mRNA vaccines Moderna/Spikevax (9459 U/mL) or Pfizer-BioNTech/Comirnaty (9181 U/mL), and reported SARS-CoV-2 infection in the last six months (8849 U/mL). The median anti-S antibody titers in the first month since the last vaccination was 8184 U/mL, which declined to 5094 U/mL at the end of six months. A strong correlation of anti-S antibodies was found with past SARS-CoV-2 infection (p < 0.001) and the type of vaccines received (p <0.001) in the workers.Conclusion: Bangladeshi migrant workers receiving booster doses of vaccine, vaccinated with mRNA vaccines, and having past SARS-CoV-2 infection, mounted higher antibody responses. However, antibody levels waned with time. These findings suggest a need for further booster doses, preferably with mRNA vaccines for migrant workers before reaching host countries.

Seroprevalence of SARS-CoV-2 antibodies among Forcibly Displaced Myanmar Nationals in Cox's Bazar, Bangladesh 2020: a population-based cross-sectional study

OBJECTIVES

The study aimed to determine the seroprevalence, the fraction of asymptomatic infections, and risk factors of SARS-CoV-2 infections among the Forcibly Displaced Myanmar Nationals (FDMNs).

DESIGN

It was a population-based two-stage cross-sectional study at the level of households.

SETTING

The study was conducted in December 2020 among household members of the FDMN population living in the 34 camps of Ukhia and Teknaf Upazila of Cox's Bazar district in Bangladesh.

PARTICIPANTS

Among 860 697 FDMNs residing in 187 517 households, 3446 were recruited for the study. One individual aged 1 year or older was randomly selected from each targeted household.

PRIMARY AND SECONDARY OUTCOME MEASURES

Blood samples from respondents were tested for total antibodies for SARS-CoV-2 using Wantai ELISA kits, and later positive samples were validated by Kantaro kits.

RESULTS

More than half (55.3%) of the respondents were females, aged 23 median (IQR 14-35) years and more than half (58.4%) had no formal education. Overall, 2090 of 3446 study participants tested positive for SARS-CoV-2 antibody. The weighted and test adjusted seroprevalence (95% CI) was 48.3% (45.3% to 51.4%), which did not differ by the sexes. Children (aged 1-17 years) had a significantly lower seroprevalence 38.6% (95% CI 33.8% to 43.4%) compared with adults (58.1%, 95% CI 55.2% to 61.1%). Almost half (45.7%, 95% CI 41.9% to 49.5%) of seropositive individuals reported no relevant symptoms since March 2020. Antibody seroprevalence was higher in those with any comorbidity (57.8%, 95% CI 50.4% to 64.5%) than those without (47.2%, 95% CI 43.9% to 50.4%). Multivariate logistic regression analysis of all subjects identified increasing age and education as risk factors for seropositivity. In children (≤17 years), only age was significantly associated with the infection.

CONCLUSIONS

In December 2020, about half of the FDMNs had antibodies against SARS-CoV-2, including those who reported no history of symptoms. Periodic serosurveys are necessary to recommend appropriate public health measures to limit transmission.