SARS-CoV-2 seroprevalence among blood donors in Uganda: 2019-2022

Longitudinal assessment of immunogenicity of inactivated COVID-19 booster immunization and breakthrough infection in blood donors: A multicenter study from 2021 to 2023

Assessing immune responses across diverse populations is essential for refining public health strategies. Blood donors offer valuable insights into community-level immunity. This study aims to investigate immune responses associated with inactivated COVID-19 booster immunization and breakthrough infections in blood donors. This study was conducted in a cohort of blood donors from six centers across five of China's seven major geographical regions, spanning from December 2021 to February 2023. Blood samples were collected before booster vaccination, at 1, 3, and 6 months post-vaccination, as well as 1 month post-infection. SARS-CoV-2-specific antibodies, T cell specific IFNγ levels, and neutralizing antibodies against wild-type and Omicron strains were measured. Platelet count, anti-PF4 antibody, and D-dimer levels were assessed. Demographic characteristics were analyzed to determine their impact on immunogenicity. SARS-CoV-2-specific antibodies and IFNγ levels significantly increased post-booster, peaking one month after immunization. Antibodies continued to decrease at six months, while IFNγ levels remained stable at this point. Pseudovirus neutralization assays revealed elevated neutralizing antibodies following the booster dose, with minimal response to the XBB.1.5 variant. Following Omicron infection, antibody and IFNγ levels surpassed that observed post-booster. Participants aged 36-49 and those over 50 exhibited weaker immune responses post-booster than those ages 18-35, while those with BMI above 28 showed lower IFNγ levels. This study demonstrates the utility of blood donor samples for tracking immunization effectiveness against emerging pathogens, and highlights enhanced immune responses after booster immunization and breakthrough infections, underscoring the need for tailored vaccination strategies for different groups.

Autoantibodies to interferon alpha, nuclear antigens, cardiolipin, and beta 2 glycoprotein 1 in a Ugandan cohort and their relation to SARS-CoV-2 infection

OBJECTIVE

Autoantibodies (AAbs) to interferon alpha, nuclear antigens, cardiolipin, and beta 2 glycoprotein 1, have been associated with COVID-19 severity. Despite relatively low COVID-19 morbidity and mortality in East and Central Africa, AAb prevalence in these populations remain understudied.

METHODS

We evaluated AAb seroprevalence in 155 Ugandans, aged 40-50, using paired samples collected before and after the onset of the COVID-19 pandemic. Among these, 117 had serological evidence of SARS-CoV-2 infection, and 38 did not. To assess the effect of SARS-CoV-2 infection on AAb prevalence, we: 1) longitudinally compared AAb prevalence before and after evidence of infection, and 2) cross-sectionally compared AAb prevalence between those with and without infection evidence at both timepoints. Associations between AAbs and health characteristics were also explored.

RESULTS

There was no difference in AAb prevalence between individuals with and without evidence of infection, nor any longitudinal change after evidence of infection. However, we observed a higher-than-expected prevalence anti-beta 2 glycoprotein 1. Additionally, anti-cardiolipin was significantly associated with reported hypertension.

CONCLUSIONS

Our findings contribute to the limited literature on AAb prevalence in East Africa and suggest that SARS-CoV-2 does not induce these AAbs.

Kaposi's sarcoma herpesvirus seroprevalence among blood donors in Uganda

BACKGROUND

Kaposi's sarcoma herpesvirus (KSHV) causes a life-long infection that can progress to several types of KSHV-associated diseases. There is evidence for transfusion transmission of KSHV. In endemic regions, such as sub-Saharan African, KSHV seroprevalence is >40%. However, previous studies of blood donors utilized immunoassays that detect KSHV-associated disease-specific antigens, which may underestimate the true burden of KSHV in a healthy population.

STUDY DESIGN AND METHODS

We utilized samples from an on-going transfusion transmitted infection clinical trial to estimate the seroprevalence of KSHV among 4921 blood donations from healthy donors in Uganda collected between October 2019 and December 2022. A multiplexed bead-based assay was used to measure plasma IgG against five antigens encoded by the K8.1, K10.5, ORF73, ORF38, and ORF25 genes of KSHV. Significant associations between donor characteristics and seroprevalence were assessed by chi-square tests.

RESULTS

Overall, KSHV seroprevalence was 69.1%. Seroprevalence was higher in units collected from older donors compared with younger donors and male donors (71.9% [95% confidence interval (CI) = 70.4%-73.3%]) compared with female donors (61.3% [95% CI = 58.6%-64.0%]; p < .001). KSHV seroprevalnce was higher among units collected from donors positive for T. pallidum (82.5% [95% CI = 73.8%-89.3%]) compared with units collected from donors who were negative (68.8% [95% CI = 67.5%-70.1%]; p < .001). KSHV seroprevalence was higher in units that tested positive for HIV, HBV, or HCV, though these results were not statistically significant.

CONCLUSION

Given the high seroprevalence and limited availability of lab assays that detect active KSHV infections, methods such as leukoreduction or pathogen reduction should be considered to potentially reduce the risk of transfusion transmission of KSHV.

A Surrogate Enzyme-Linked Immunosorbent Assay to Select High-Titer Human Convalescent Plasma for Treating Immunocompromised Patients Infected With Severe Acute Respiratory Syndrome Coronavirus 2 Variants of Concern

BACKGROUND

The emergence of new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants challenges the treatment of immunocompromised patients against coronavirus disease 2019 (COVID-19). High-titer COVID-19 convalescent plasma (CCP) remains one of the few available therapeutics for these patients. We have revisited the selection of CCP samples and evaluated their efficacy against the Omicron XBB.1.5 variant, the dominant strain in 2023.

METHODS

A surrogate enzyme-linked immunoassay was reviewed to select CCP samples that ensure a protective level of neutralizing antibodies as the main correlate of protection. Antibody titers were analyzed in 500 serum samples from a population-based serosurvey at Mount Sinai Hospital in early 2023, and the results were validated with CCP samples (collected in 2020-2023) using an immunosuppressed mouse model.

RESULTS

Using logistic regression modeling, we have redefined high-titer CCP against the new variant in the postpandemic era, where over 97% of the population has natural or vaccine-induced antibodies against earlier SARS-CoV-2 strains. Treatment of immunocompromised mice with two doses (100 μL/dose) of CCP plasma via intraperitoneal injection reduced lung viral titers by 46-fold 3 days post-XBB.1.5 infection.

CONCLUSIONS

These findings will guide future efforts in selecting high-titer CCP for emerging SARS-CoV-2 variants.

SARS-CoV-2 Anti-S an Anti-N IgG Seropositivity in Children and Young People (1-24 Years) According to HIV Status in Lomé (Togo) in 2022

We aimed to estimate SARS-CoV-2 seropositivity among children and young people in Lomé, Togo, according to HIV status. A multicenter comparative cross-sectional study was conducted, and 636 participants were included (41.8% living with HIV). Anti-S (88.7% vs. 89.1%) and anti-N (41.6% vs. 39.5%) IgG seropositivity were comparable in both groups. These data suggest no increased COVID-19 susceptibility in children and young people with HIV.

Seroprevalence of SARS-CoV-2 and risk factors for infection among children in Uganda: A serial cross-sectional study

BACKGROUND

Understanding COVID-19's impact on children is vital for public health policy, yet age-specific data is scarce, especially in Uganda. This study examines SARS-CoV-2 seroprevalence and risk factors among Ugandan children at two timepoints, along with COVID-19-related knowledge and practices in households, including adult vaccination status.

METHODS

Baseline surveys were conducted in 12 communities from April to May 2021 (post-Alpha wave) and follow-up surveys in 32 communities from November 2021 to March 2022 (Omicron wave). Household questionnaires and blood samples were collected to test for malaria by microscopy and for SARS-CoV-2 using a Luminex assay. Seroprevalence was estimated at both the survey and community level. Mixed-effects logistic regression models assessed the association between individual and household factors and SARS-CoV-2 seropositivity in children, adjusting for household clustering.

RESULTS

More households reported disruptions in daily life at baseline compared to follow-up, though economic impacts lingered. By the follow-up survey, 52.7% of adults had received at least one COVID-19 vaccine dose. Overall seroprevalence in children was higher at follow-up compared to baseline (71.6% versus 19.2%, p < 0.001). Seroprevalence in children ranged across communities from 6-37% at baseline and 50-90% at follow-up. At baseline, children from the poorest households were more likely to be infected. Increasing age remained the only consistent risk factor for SARS-CoV-2 seroconversion at both timepoints.

CONCLUSIONS

Results indicate that a larger number of children were infected during the Delta and Omicron waves of COVID-19 compared to the Alpha wave. This study is the largest seroprevalence survey in children in Uganda, providing evidence that most children were infected with SARS-CoV-2 before the vaccine was widely available to pediatric populations. Pediatric infections were vastly underreported by case counts, highlighting the importance of seroprevalence surveys in assessing disease burden when testing and reporting rates are limited and many cases are mild or asymptomatic.

SARS-CoV-2 seroprevalence in people living with HIV in South Sudan

Objectives

The burden of SARS-CoV-2 infection in people living with HIV (PLHIV) in South Sudan is unknown.

Methods

We conducted a cross-sectional seroprevalence survey of SARS-CoV-2 immunoglobulin (Ig) G antibodies and other diseases of public health importance (strongyloidiasis, toxoplasmosis) in PLHIV in South Sudan during April 1, 2020-April 30, 2022. We used a multiplex SARS-CoV-2 immunoassay to detect IgG antibodies targeting the SARS-CoV-2 spike, receptor binding domain, and nucelocapsid (N) proteins, and antigens for other pathogens (Strongyloides stercoralis and Toxoplasma gondii).

Results

Among 3518 samples tested, seroprevalence of IgG antibodies to SARS-CoV-2 spike protein and receptor binding domain 591 and nucleocapsid ranged from 1.4% (95% confidence interval [CI]: 0.9-2.1%) in April-June 2020 to 53.3% (95% CI: 49.5-57.1%) in January-March 2022. The prevalence of S. stercoralis IgG ranged between 27.3% (95% CI: 23.4-31.5%) in October-December 2021 and 47.2% (95% CI: 37.8-56.8%) in July-September 2021, and, for T. gondii IgG, prevalence ranged from 15.5% (95% CI: 13.3-17.9%) in April-June 2020 to 36.2% (95% CI: 27.4-46.2%) July-September 2021.

Conclusions

By early 2022, PLHIV in South Sudan had high rates of SARS-CoV-2 seropositivity. Surveillance of diseases of global health concern in PLHIV is crucial to estimate population-level exposure and inform public health responses.

Detection of Nucleocapsid Antibodies Associated with Primary SARS-CoV-2 Infection in Unvaccinated and Vaccinated Blood Donors

Nucleocapsid antibody assays can be used to estimate SARS-CoV-2 infection prevalence in regions implementing spike-based COVID-19 vaccines. However, poor sensitivity of nucleocapsid antibody assays in detecting infection after vaccination has been reported. We derived a lower cutoff for identifying previous infections in a large blood donor cohort (N = 142,599) by using the Ortho VITROS Anti-SARS-CoV-2 Total-N Antibody assay, improving sensitivity while maintaining specificity >98%. We validated sensitivity in samples donated after self-reported swab-confirmed infections diagnoses. Sensitivity for first infections in unvaccinated donors was 98.1% (95% CI 98.0-98.2) and for infection after vaccination was 95.6% (95% CI 95.6-95.7) based on the standard cutoff. Regression analysis showed sensitivity was reduced in the Delta compared with Omicron period, in older donors, in asymptomatic infections, <30 days after infection, and for infection after vaccination. The standard Ortho N antibody threshold demonstrated good sensitivity, which was modestly improved with the revised cutoff.

SARS-CoV-2 seropositivity in African women living with HIV and their infants

BACKGROUND

SARS-CoV-2 seropositivity data in women living with HIV (WLHIV), their infants and associated factors in this subpopulation remain limited. We retrospectively measured SARS-CoV-2 seropositivity from 07/2020-11/2021 among WLHIV and their children in the PROMOTE observational cohort in Uganda, Malawi, and Zimbabwe prior to widespread SARS-CoV-2 vaccination in those countries.

METHODS

Plasma stored during 3 waves of the COVID-19 pandemic in East/Southern Africa were tested for SARS-CoV-2 specific IgG antibodies (Ab) using serological assays that detect adaptive immune responses to SARS-CoV-2 spike protein. (EUROIMMUN, Mountain Lakes, New Jersey and Roche Diagnostics, Indianapolis, IN). Modified-Poisson regression models were used to calculate prevalence rate ratios (PRR) and 95% confidence intervals (CI) to identify sociodemographic and clinical risk factors.

RESULTS

PROMOTE samples from 918 mothers and 1237 children were analysed. Overall, maternal SARS-CoV-2 seropositivity was 60.1% (95% CI: 56.9 -63.3) and 41.5% (95%CI: 38.8 - 44.2) for children. Non-breastfeeding mothers had a 31% higher risk of SARS-CoV-2 seropositivity compared to breastfeeding mothers (aPRR=1.31, 95%CI: 1.08-1.59). WLHIV with undetectable viral load had a 10% increased risk of SARS-CoV-2 seropositivity (aPRR=1.10, 95%CI: 0.89-1.37). Moreover, those who were normotensive had 12% increased risk SARS-CoV-2 seropositivity (aPRR= 1.12, 95% CI: 0.68-1.85) compared to women with hypertension. Children between 2 and 5 years had a 19% reduced risk of SARS-CoV-2 seropositivity (aPRR=0.81, 95%CI: 0.64-1.02) when compared to younger children. Mother/infant SARS-CoV-2 serostatuses were discordant in 346/802 (43.1%) families tested: mothers+/children- in 72.3%; mothers-/children+ in 26.3%; child+/sibling+ concordance was 34.6%.

CONCLUSIONS

These SARS-CoV-2 seropositivity data indicate that by late 2021, about 60% of mothers and about 40% of children in a cohort of HIV-affected families in eastern/southern Africa had been infected with SARS-CoV-2. More mothers than their infants tested SARS-CoV-2+, likely due to a greater external exposure for mothers linked to daily routines/employment, and school closures. Breastfeeding was protective for mothers, likely because of higher likelihood of staying home with young children, and thus less exposure. Discordant results between children within the same families underscores the need to further understand transmission dynamics within households.

Seroprevalence of SARS-CoV-2 and risk factors for infection among children in Uganda: a serial cross-sectional study

Background

Understanding COVID-19's impact on children is vital for public health policy, yet age-specific data is scarce, especially in Uganda. This study examines SARS-CoV-2 seroprevalence and risk factors among Ugandan children at two timepoints, along with COVID-19-related knowledge and practices in households, including adult vaccination status.

Methods

Baseline surveys were conducted in 12 communities from April to May 2021 (post-Alpha wave) and follow-up surveys in 32 communities from November 2021 to March 2022 (Omicron wave). Household questionnaires and blood samples were collected to test for malaria by microscopy and for SARS-CoV-2 using a Luminex assay. Seroprevalence was estimated at both the survey and community level. Mixed-effects logistic regression models assessed the association between individual and household factors and SARS-CoV-2 seropositivity in children, adjusting for household clustering.

Results

More households reported disruptions in daily life at baseline compared to follow-up, though economic impacts lingered. By the follow-up survey, 52.7% of adults had received at least one COVID-19 vaccine dose. Overall seroprevalence in children was higher at follow-up compared to baseline (71.6% versus 19.2%, p < 0.001). Seroprevalence in children ranged across communities from 6-37% at baseline and 50-90% at follow-up. At baseline, children from the poorest households were more likely to be infected. Increasing age remained the only consistent risk factor for SARS-CoV-2 seroconversion at both timepoints.

Conclusions

Results indicate that a larger number of children were infected by the Delta and Omicron waves of COVID-19 compared to the Alpha wave. This study is the largest seroprevalence survey in children in Uganda, providing evidence that most children were infected with SARS-CoV-2 before the vaccine was widely available to pediatric populations. Pediatric infections were vastly underreported by case counts, highlighting the importance of seroprevalence surveys in assessing disease burden when testing and reporting rates are limited and many cases are mild or asymptomatic.

High pre-Delta and early-Omicron SARS-CoV-2 seroprevalence detected in dried blood samples from Kinshasa (D.R. Congo)

Studies on the impact of the COVID-19 pandemic in sub-Saharan Africa have yielded varying results, although authors universally agree the real burden surpasses reported cases. The primary objective of this study was to determine SARS-CoV-2 seroprevalence among patients attending Monkole Hospital in Kinshasa (D.R. Congo). The secondary objective was to evaluate the analytic performance of two chemiluminescence platforms: Elecsys® (Roche) and VirClia® (Vircell) on dried blood spot samples (DBS). The study population (N = 373) was recruited in two stages: a mid-2021 blood donor cohort (15.5% women) and a mid-2022 women cohort. Crude global seroprevalence was 61% (53.9%-67.8%) pre-Delta in 2021 and 90.2% (84.7%-94.2%) post-Omicron in 2022. Anti-spike (S) antibody levels significantly increased from 53.1 (31.8-131.3) U/mL in 2021 to 436.5 (219.3-950.5) U/mL in 2022 and were significantly higher above 45 years old in the 2022 population. Both platforms showed good analytic performance on DBS samples: sensitivity was 96.8% for IgG (antiN/S) (93.9%-98.5%) and 96.0% (93.0%-98.0%) for anti-S quantification. These results provide additional support for the notion that exposure to SARS-CoV-2 is more widespread than indicated by case-based surveillance and will be able to guide the pandemic response and strategy moving forward. Likewise, this study contributes evidence to the reliability of DBS as a tool for serological testing and diagnosis in resource-limited settings.