The seroprevalence of severe acute respiratory syndrome coronavirus 2 in Delhi, India: a repeated population-based seroepidemiological study

Dynamics of SARS-CoV-2 seroassay sensitivity: a systematic review and modelling study

BackgroundSerological surveys have been the gold standard to estimate numbers of SARS-CoV-2 infections, the dynamics of the epidemic, and disease severity. Serological assays have decaying sensitivity with time that can bias their results, but there is a lack of guidelines to account for this phenomenon for SARS-CoV-2.AimOur goal was to assess the sensitivity decay of seroassays for detecting SARS-CoV-2 infections, the dependence of this decay on assay characteristics, and to provide a simple method to correct for this phenomenon.MethodsWe performed a systematic review and meta-analysis of SARS-CoV-2 serology studies. We included studies testing previously diagnosed, unvaccinated individuals, and excluded studies of cohorts highly unrepresentative of the general population (e.g. hospitalised patients).ResultsOf the 488 screened studies, 76 studies reporting on 50 different seroassays were included in the analysis. Sensitivity decay depended strongly on the antigen and the analytic technique used by the assay, with average sensitivities ranging between 26% and 98% at 6 months after infection, depending on assay characteristics. We found that a third of the included assays departed considerably from manufacturer specifications after 6 months.ConclusionsSeroassay sensitivity decay depends on assay characteristics, and for some types of assays, it can make manufacturer specifications highly unreliable. We provide a tool to correct for this phenomenon and to assess the risk of decay for a given assay. Our analysis can guide the design and interpretation of serosurveys for SARS-CoV-2 and other pathogens and quantify systematic biases in the existing serology literature.

Trajectories of Seroprevalence and Neutralizing Activity of Antibodies against SARS-CoV-2 in Southern Switzerland between July 2020 and July 2021: An Ongoing, Prospective Population-Based Cohort Study

OBJECTIVES

The COVID-19 pandemic continues, and evidence on infection- and vaccine-induced immunity is key. We assessed COVID-19 immunity and the neutralizing antibody response to virus variants across age groups in the Swiss population.

STUDY DESIGN

We conducted a cohort study in representative community-dwelling residents aged five years or older in southern Switzerland (total population 353,343), and we collected blood samples in July 2020 (in adults only, N = 646), November-December 2020 (N = 1457), and June-July 2021 (N = 885).

METHODS

We used a previously validated Luminex assay to measure antibodies targeting the spike (S) and the nucleocapsid (N) proteins of the virus and a high-throughput cell-free neutralization assay optimized for multiple spike protein variants. We calculated seroprevalence with a Bayesian logistic regression model accounting for the population's sociodemographic structure and the test performance, and we compared the neutralizing activity between vaccinated and convalescent participants across virus variants.

RESULTS

The overall seroprevalence was 7.8% (95% CI: 5.4-10.4) by July 2020 and 20.2% (16.4-24.4) by December 2020. By July 2021, the overall seroprevalence increased substantially to 72.5% (69.1-76.4), with the highest estimates of 95.6% (92.8-97.8) among older adults, who developed up to 10.3 more antibodies via vaccination than after infection compared to 3.7 times more in adults. The neutralizing activity was significantly higher for vaccine-induced than infection-induced antibodies for all virus variants (all p values < 0.037).

CONCLUSIONS

Vaccination chiefly contributed to the reduction in immunonaive individuals, particularly those in older age groups. Our findings on the greater neutralizing activity of vaccine-induced antibodies than infection-induced antibodies are greatly informative for future vaccination campaigns.

COVID-19 infection, and reinfection, and vaccine effectiveness against symptomatic infection among health care workers in the setting of omicron variant transmission in New Delhi, India

Background

Surge of SARS CoV-2 infections ascribed to omicron variant began in December 2021 in New Delhi. We determined the infection and reinfection density in a cohort of health care workers (HCWs) along with vaccine effectiveness (VE) against symptomatic infection within omicron transmission period (considered from December 01, 2021 to February 25, 2022.

Methods

This is an observational study from the All India Institute of Medical Sciences, New Delhi. Data were collected telephonically. Person-time at risk was counted from November 30, 2021 till date of infection/ reinfection, or date of interview. Comparison of clinical features and severity was done with previous pandemic periods. VE was estimated using test-negative case-control design [matched pairs (for age and sex)]. Vaccination status was compared and adjusted odds ratios (OR) were computed by conditional logistic regression. VE was estimated as (1-adjusted OR)X100-.

Findings

11474 HCWs participated in this study. The mean age was 36⋅2 (±10⋅7) years. Complete vaccination with two doses were reported by 9522 (83%) HCWs [8394 (88%) Covaxin and 1072 Covishield (11%)]. The incidence density of all infections and reinfection during the omicron transmission period was 34⋅8 [95% Confidence Interval (CI): 33⋅5-36⋅2] and 45⋅6 [95% CI: 42⋅9-48⋅5] per 10000 person days respectively. The infection was milder as compared to previous periods. VE was 52⋅5% (95% CI: 3⋅9-76⋅5, p = 0⋅036) for those who were tested within 14-60 days of receiving second dose and beyond this period (61-180 days), modest effect was observed.

Interpretation

Almost one-fifth of HCWs were infected with SARS CoV-2 during omicron transmission period, with predominant mild spectrum of COVID-19 disease. Waning effects of vaccine protection were noted with increase in time intervals since vaccination.

Funding

None.

SARS-CoV-2 Seroprevalence in Delhi, India, During September-October 2021: A Population-Based Seroepidemiological Study

Background

A previous community-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serosurvey in Delhi in January 2021 reported a seroprevalence of 50.52%. We conducted a repeat serosurvey to obtain a recent estimate of the seroprevalence of IgG SARS-CoV-2 in the general population of Delhi, India.

Methods

This cross-sectional study was conducted from September 24 to October 14, 2021, in 274 wards of Delhi among 27,811 participants through a multistage sampling technique.

Results

The crude seroprevalence was 89.5% (95% CI 89.1, 89.8), weight for age and sex was 88% (95% CI 87.6, 88.4), and after adjustment for assay performance was estimated as 97.5% (95% CI 97.0, 98.0). On adjusted analysis, the odds of seroconversion in the participants vaccinated with at least one dose of either COVID-19 vaccine (Covishield/Covaxin) was more than four times compared to the unvaccinated ones (aOR 4.2 (3.8, 4.6)). 86.8% of the seropositive individuals had a SARS-CoV-2 signal/cut-off ≥4.0 although it was significantly lower in the pediatric age group. Post-second wave (August to October 2021), on average there were daily 39 new COVID-19 cases and 0.44 deaths which during Omicron driven the third wave in January to March 2022 increased to daily 4,267 cases and 11.6 deaths.

Conclusion

A high prevalence of IgG antibodies against SARS-CoV-2 with likely higher antibody titres in the vaccinated compared to the unvaccinated groups with evidence of hybrid immunity in a majority of the population was protective against severe disease during transmission of subsequent omicron variants.

Seroprevalence of COVID-19 in Blood Donors: A Systematic Review and Meta-Analysis

Introduction

Determining the prevalence of SARS-CoV-2 in blood donors makes the control of virus circulation possible in healthy people and helps implement strategies to reduce virus transmission. The purpose of the study was to examine the seroprevalence of COVID-19 in blood donors using systematic review and meta-analysis.

Materials and Methods

The electronic databases PubMed, Scopus, Web of Science, and the Google Scholar search engine were searched using standard keywords up to 2022-04-26. The variance of each study was calculated according to the binomial distribution. Studies were combined according to the sample size and variance. Q Cochrane test and I2 index were used to examine the heterogeneity of the studies. Data analysis was performed in STATA 14 software, and the significance level of the tests was P < 0.05.

Results

In the 28 papers examined with 227894 samples, the seroprevalence of COVID-19 in blood donors was 10% (95% CI: 9%, 11%), estimated 5% (95% CI: 4%, 7%) among men and 6% (95% CI: 4%, 7%) among women. This rate in different blood groups was as follows: A 12% (95% CI: 10%-14%), B 12% (95% CI: 10%-15%), AB 9% (95% CI: 7%-12%), and O 13% (95% CI: 11%-16%). The seroprevalence of COVID-19 in blood donors in North America 10%, Europe 7%, Asia 23%, South America 5%, and Africa was 4%; Moreover, the seroprevalence of IgG antibodies was estimated to be 23% (95% CI: 18%-29%) and IgM 29% (95% CI: 9%-49%).

Conclusion

The highest prevalence of COVID-19 serum in women blood donors was among blood group O and Asia. The seroprevalence of IgG and IgM antibodies was high too.

Assessing the burden of COVID-19 in developing countries: systematic review, meta-analysis and public policy implications

INTRODUCTION

The infection fatality rate (IFR) of COVID-19 has been carefully measured and analysed in high-income countries, whereas there has been no systematic analysis of age-specific seroprevalence or IFR for developing countries.

METHODS

We systematically reviewed the literature to identify all COVID-19 serology studies in developing countries that were conducted using representative samples collected by February 2021. For each of the antibody assays used in these serology studies, we identified data on assay characteristics, including the extent of seroreversion over time. We analysed the serology data using a Bayesian model that incorporates conventional sampling uncertainty as well as uncertainties about assay sensitivity and specificity. We then calculated IFRs using individual case reports or aggregated public health updates, including age-specific estimates whenever feasible.

RESULTS

In most locations in developing countries, seroprevalence among older adults was similar to that of younger age cohorts, underscoring the limited capacity that these nations have to protect older age groups.Age-specific IFRs were roughly 2 times higher than in high-income countries. The median value of the population IFR was about 0.5%, similar to that of high-income countries, because disparities in healthcare access were roughly offset by differences in population age structure.

CONCLUSION

The burden of COVID-19 is far higher in developing countries than in high-income countries, reflecting a combination of elevated transmission to middle-aged and older adults as well as limited access to adequate healthcare. These results underscore the critical need to ensure medical equity to populations in developing countries through provision of vaccine doses and effective medications.

Reassessing Reported Deaths and Estimated Infection Attack Rate during the First 6 Months of the COVID-19 Epidemic, Delhi, India

India reported >10 million coronavirus disease (COVID-19) cases and 149,000 deaths in 2020. To reassess reported deaths and estimate incidence rates during the first 6 months of the epidemic, we used a severe acute respiratory syndrome coronavirus 2 transmission model fit to data from 3 serosurveys in Delhi and time-series documentation of reported deaths. We estimated 48.7% (95% credible interval 22.1%-76.8%) cumulative infection in the population through the end of September 2020. Using an age-adjusted overall infection fatality ratio based on age-specific estimates from mostly high-income countries, we estimated that just 15.0% (95% credible interval 9.3%-34.0%) of COVID-19 deaths had been reported, indicating either substantial underreporting or lower age-specific infection-fatality ratios in India than in high-income countries. Despite the estimated high attack rate, additional epidemic waves occurred in late 2020 and April-May 2021. Future dynamics will depend on the duration of natural and vaccine-induced immunity and their effectiveness against new variants.

Reassessing Reported Deaths and Estimated Infection Attack Rate during the First 6 Months of the COVID-19 Epidemic, Delhi, India

India reported >10 million coronavirus disease (COVID-19) cases and 149,000 deaths in 2020. To reassess reported deaths and estimate incidence rates during the first 6 months of the epidemic, we used a severe acute respiratory syndrome coronavirus 2 transmission model fit to data from 3 serosurveys in Delhi and time-series documentation of reported deaths. We estimated 48.7% (95% credible interval 22.1%-76.8%) cumulative infection in the population through the end of September 2020. Using an age-adjusted overall infection fatality ratio based on age-specific estimates from mostly high-income countries, we estimated that just 15.0% (95% credible interval 9.3%-34.0%) of COVID-19 deaths had been reported, indicating either substantial underreporting or lower age-specific infection-fatality ratios in India than in high-income countries. Despite the estimated high attack rate, additional epidemic waves occurred in late 2020 and April-May 2021. Future dynamics will depend on the duration of natural and vaccine-induced immunity and their effectiveness against new variants.

A Comparative Analysis of COVID-19 IgG Antibody Level and Socio-Demographic Status in Symptomatic and Symptomatic Population of South Andaman, India

Introduction: The serosurveillance of COVID-19 antibody levels and their difference between symptomatic and asymptomatic groups can help in understanding the immune status of the community and the factors affecting it. Hence, the study was undertaken to find the differences between these two groups with respect to antibodies level and other socio-demographic variables in the South Andaman district.

Methods: A population-based serosurveillance study covering more than 4,000 samples was carried out in the South Andaman district. The participants were selected by multistage cluster sampling. The venous blood samples were tested for IgG COVID-19 antibodies by Erba Lisa Elisa kit.

Results: 5.3% of total individuals (217) were symptomatic whereas 94.7% (3,872) were asymptomatic. The symptomatic individuals had lower antibodies (33.6%) as compared to asymptomatic individuals (40.1%) (p-value=0.059). In the age group of 31-45 years, antibody positivity in the asymptomatic group was significantly higher than in the symptomatic group (p-value 0.031). The antibody positivity was higher in moderate to severe cases who needed hospital admission. The antibody positivity was found similar in both the groups in front-line workers as well as in non-front-line workers (p-value=0.104, 0.274, respectively).

Conclusion: The antibody positivity was higher in asymptomatic individuals as compared to symptomatic individuals, particularly in the age group of 31-45 years. The higher level of antibody positivity in asymptomatic individuals reflected a stronger immune response which led to no clinical manifestations. The antibody positivity was also found higher in moderate to severe cases undergoing hospital admission whereas antibodies positivity was found similar in front-line and non-front-line workers.

Seroprevalence of Anti-SARS-CoV-2 IgG Antibodies among HIV Infected Individuals Attending ART Centre at Pune: A Cross-Sectional Study

Background: We aimed to determine the anti-SARS-CoV-2 IgG antibodies among people living with HIV (PLHIV) in Pune, India. Methods: This cross-sectional study was conducted between March 2021 and June 2021. Demographic and clinical information related to coronavirus disease 2019 (COVID-19) were recorded on structured questionnaires. Blood samples were collected and tested for anti-SARS-CoV-2 IgG antibodies using commercial ELISA. Results: Of the 405 HIV infected individuals enrolled in the study, 223(55.1%) were females. Mean age and CD4 count of participants were 42 years (SD: 10) and 626 cells/mm³ (SD: 284) respectively. A total of 382 (95%) PLHIV were virologically suppressed. The seropositivity against SARS-CoV-2 was found in 221 PLHIV (54.6%, 95% CI: 49.7-59.4). No significant association was found between demographic or clinical factors and seropositivity. Conclusion: A high prevalence of anti-SARS-CoV-2 IgG antibodies was found among PLHIV attending ART centre indicating an exposure to the virus among them.

Anti-factor H antibody associated hemolytic uremic syndrome following SARS-CoV-2 infection

BACKGROUND

The pathogenesis of autoantibody generation in anti-factor H (FH) antibody associated atypical hemolytic uremic syndrome (aHUS) is unknown and is perhaps triggered by an infectious or environmental agent. We observed an unusual increase of patients with anti-FH antibody associated aHUS coinciding with the second pandemic wave in New Delhi and suspected that SARS-CoV-2 infection might be a potential trigger.

METHODS

We screened for SARS-CoV-2 infection using reverse transcriptase polymerase chain reaction (RT-PCR) and serology in 13 consecutive patients with anti-FH antibody associated aHUS during the past year in New Delhi.

RESULTS

We report 5 patients, 4-13 years old, who presented with a febrile illness without respiratory symptoms during the second pandemic wave. Of these, 3 patients presented with a relapse 25-85 months following the initial episode of aHUS. SARS-CoV-2 was detected by RT-PCR in 1 patient and by serology in 4 patients (median titer 47.1 cut-off index). Patients had high titers of anti-FH antibodies (median 2,300 AU/ml). Genetic studies, done in 3 of the 5 patients, showed homozygous CFHR1 deletion without other significant genetic abnormalities. Specific management comprised plasma exchanges and oral prednisolone, combined with either cyclophosphamide or mycophenolate mofetil. At median follow-up of 3.3 months, the estimated glomerular filtration rate in 4 patients ranged from 62 to 110 ml/min/1.73 m²; one patient was dialysis-dependent.

CONCLUSION

Increased vigilance is required during the pandemic, especially in patients with anti-FH associated aHUS, who might relapse despite quiescent disease for a prolonged period. A higher resolution version of the Graphical abstract is available as Supplementary information.

Seroprevalence of Anti-SARS-CoV-2 Antibodies among Municipal Staff in the Municipality of Prishtina

BACKGROUND

Some studies have assessed the seroprevalence of anti-SARS-CoV-2 antibodies in different populations. Very few studies have explored seroprevalence in municipal workers, an important and potentially high-risk population. This study aims to determine the prevalence of anti-SARS-CoV-2 antibodies in municipal workers, with the additional examination of the association of prevalence with various demographic, health-related, and epidemiological factors.

METHODS

We surveyed and tested for seroprevalence 418 public servants from the municipality of Prishtina, the capital of Kosovo. The primary prespecified outcome was the seroprevalence of anti-SARS-CoV-2 antibodies, IgG, and IgM. Additional outcomes were crude and adjusted odds ratios of seroprevalence by different factors.

RESULTS

21.1% of municipal workers tested positive for either IgM or IgG. Of these, 9.6% were positive for IgM and 19.4% for IgG. Data showed high levels of adherence to protective measures, e.g., social distancing in the office, but calculation of ORs did not show a significant difference between those reporting adherence to such measures and those reporting nonadherence. Of other examined factors, significantly lower odds were observed for smokers (0.52, 95% CI 0.28, 0.97), while municipal workers with infected family members had elevated odds of seropositivity according to both crude (2.19, 95% CI 1.34, 3.59) and adjusted (2.00, 95% CI 1.17, 3.41) ORs.

CONCLUSIONS

Most answers from public servants demonstrated compliance to social-distancing policies in the workplace, but analysis of crude and adjusted odds ratios did not suggest a significant effect between municipal workers who followed these guidelines and those who did not. Results from this study help Kosovo policy makers in understanding the level of prevalence of COVID-19 in municipal workers and the effect of different factors on such prevalence. Results from the study could inform future decisions on the design and application of protective measures for municipal workers. Our findings should encourage further research to assess the extent of the spread of COVID-19 to other essential workers in Kosovo, including retail workers.

SARS-Coronavirus-2 seroprevalence in asymptomatic healthy blood donors: Indicator of community spread

Background

The Corona virus disease 2019 (COVID-19) pandemic caused by SARS -Corona virus-2 (SARS-CoV-2) has been a major concern the world over. Serological surveillance is an important tool to assess the spread of infection in the community. This study attempted to assess the prevalence of antibodies to SARS-CoV-2 among blood donors in Delhi, India during the pre-vaccination period.

Methods

Seroprevalence of SARS-CoV2-2 IgG antibodies were determined in blood donors reporting to the Department of Transfusion medicine at a tertiary care hepatobiliary center, in India from September to October 2020. The SARS-CoV-2 IgG antibodies against spike subunit 1 protein were measured using the enhanced chemiluminescence method.

Results

A total of 1066 blood donors were screened. The overall seropositivity for SARS-CoV-2 IgG antibodies was 27.57 % (294/1066). The highest seropositivity was seen in the age group 26−35 years, 46.6 % (137/492), followed by 18−25 years, 28.2 % (83/260), 36−45 years, 19.4 % (57/244), and more than 45 years, 5.8 % (17/70). The seropositivity in the donors who had donated blood previously was 26.1 % (189/723). There was no statistically significant difference amongst seroprevalence in the blood groups, AB blood group (32.6 %, 95 % CI 23.02−43.3), group B (27.2 %, 95 % CI 22.8−32.09 %), group A (27.1 %, 95 % CI 21.8−32.9 %), and group O (27.02 %, 95 % CI 22.3−32.1 %) (p 0.539).

Conclusions

There was significantly higher seropositivity for SARS-CoV-2 antibodies in the voluntary healthy blood donors indicating community spread and large number of asymptomatic cases in Delhi. Higher seroprevalence in younger adults indicated increased exposure to the virus and lack of COVID appropriate behaviour.

Second Wave of the COVID-19 Pandemic in Delhi, India: High Seroprevalence Not a Deterrent?

Background We report the findings of a large follow-up, community-based, cross-sectional serosurvey and correlate it with the coronavirus disease (COVID-19) test-positivity rate and the caseload observed between the peaks of the first and the second wave of the COVID-19 pandemic in Delhi, India. Methodology Individuals aged five and above were recruited from 274 wards of the state (population approximately 19.6 million) from January 11 to January 22, 2021. A total of 100 participants each were included from all wards for a net sample size of approximately 28,000. A multistage sampling technique was employed to select participants for the household serosurvey. Anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin (IgG) antibodies were detected by using the VITROS® (Ortho Clinical Diagnostics, Raritan, NJ, USA) assay (90% sensitivity, 100% specificity). Results Antibody positivity was observed in 14,298 (50.76%) of 28,169 samples. The age, sex, and district population-weighted seroprevalence of the SARS-CoV-2 IgG was 50.52% (95% confidence interval [CI] = 49.94-51.10), and after adjustment for assay characteristics, it was 56.13% (95% CI = 55.49-56.77). On adjusted analysis, participants aged ≥50 years, of female gender, housewives, having ever lived in containment zones, urban slum dwellers, and diabetes or hypertensive patients had significantly higher odds of SARS-CoV-2 antibody positivity. The peak infection rate and the test-positivity rate since October 2020 were initially observed in mid-November 2020, with a subsequent steep declining trend, followed by a period of persistently low case burden lasting until the first week of March 2021. This was followed by a steady increase followed by an exponential surge in infections from April 2021 onward culminating in the second wave of the pandemic. Conclusions The presence of infection-induced immunity from SARS-CoV-2 even in more than one in two people can be ineffective in protecting the population. Despite such high seroprevalence, population susceptibility to COVID-19 can be accentuated by variants of concern having the ability for rapid transmission and depletion of antibody levels with the threat of recurrent infections, signifying the need for mass vaccination.