COVID-Kavach-Based Seropositivity in the General Population of Ahmedabad: Just Before the Start of the Vaccination for the Elderly in India.

Background The present study was carried out in succession of three serosurvey studies carried out during 2020 in Ahmedabad with an objective to estimate the seroprevalence of immunoglobulin G (IgG) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV2) in Ahmedabad city so as to scientifically understand the pandemic progression. Methods Polio booth-based stratification was followed for the population-based stratified sampling among the general population of Ahmedabad. The seroprevalence was compared with various factors for valid and precise predictions regarding the immunity status of the population. Results As on February 2021, the seroprevalence for IgG antibodies against SARS-CoV2 in the general population of Ahmedabad was 27.92% (95% confidence interval 27.06-28.80), much below the minimum desired for herd immunity. Comparison of seropositivity with age groups showed higher seroprevalence with increasing age groups. Seroprevalence was higher among males (29.08%) than females (27.01%) and the difference was statistically significant (Z=2.30, P=0.02). Calculating the seropositivity among the subcategories, cases had a seropositivity of 64.90% and family contacts had a seropositivity of 28.00%. Seronegative cases indicate the possibility of absent, undetectable, or disappearing IgG antibodies. Seropositivity of 37% among the vaccinated individuals may be related to dose and duration of vaccination, as the COVID vaccination had started just before the present study and none had completed 14 days after the second dose. Conclusions The low level of IgG antibodies against SARS-CoV2 using the COVID-Kavach test kit in the general population of Ahmedabad city of India, as on February 2021, before the start of COVID vaccination for the general population suggests that the preventive measures be strongly followed for continued control of the pandemic situation at least till majority of the population is effectively covered with vaccination.

Immunoglobulin-G Antibodies against Severe Acute Respiratory Syndrome - Coronavirus-2 among Health-Care Workers: A Serosurveillance Study from India.

Background: Seropositivity among health-care workers (HCWs) may help in better understanding of the immune response after COVID-19 infection. Objectives: To estimate seropositivity among HCWs and to compare available variables with seropositivity to understand the factors affecting seropositivity. Materials and Methods: A serosurveillance among HCWs was carried out using population proportion sampling during the second half of October 2020 in the city of Ahmedabad using the Covid-Kavach (immunoglobulin G [IgG] ELISA Antibody testing kit). Simple proportions and appropriate statistical tests were used as needed. Results: As on October' 2020, HCWs in Ahmedabad demonstrated a seropositivity of 20.84% (95% confidence interval [CI] 19.00-22.81%). Seropositivity among HCWs was lower than that of the general population (24.20%) which was estimated as part of the same study. Female HCWs had higher seropositivity 22.14% (95% CI 19.74-24.74%) as compared to 18.82% (95% CI 16.06-21.93%) among male HCWs and the difference was statistically not significant (Z = 1.66, P = 0.097). Age groups with increasing age show increasing trend in the seropositivity among HCWs. Conclusion: As on October 2020, with 20.84% seropositivity among HCWs in Ahmedabad, one in every five HCW already demonstrate IgG antibodies against severe acute respiratory syndrome- coronavirus-2. Further scientific studies on seropositivity and the factors affecting the seropositivity may be carried out to uncover more details of immune reaction after COVID-19 infection.

Seroprevalence of Immunoglobulin-G Antibody Among Confirm Cases of COVID-19.

Background Sero-surveillance to find the presence of IgG antibodies among COVID-19 cases helps in the better understanding of the immune response after COVID-19 infection. Objectives To estimate seropositivity among confirmed COVID-19 cases and to correlate the seropositivity with various factors affecting seropositivity. Methods Population-based sero-surveillance among COVID-19 cases was carried out during the second half of August 2020 in Ahmedabad using the COVID KAVACH, Immunoglobulin-G (IgG) Antibody Detection Enzyme-Linked Immunosorbent Assay (ELISA) kits. Seropositivity among cases was measured and compared with various other factors to understand the immunity status among COVID-19 cases. Results With 1073 positive for IgG antibodies from 1720 samples, the seropositivity among COVID-19 cases is 62.38% [95%CI 60.07-64.64%]. The difference in seropositivity based on gender was statistically not significant (Z=0.26, P=0.79). Children have the highest seropositivity (94.44%) and from young adults, to the elderly, the proportion of positivity among cases shows an increasing trend. Time gap analysis from the date of diagnosis shows that the proportion of cases with IgG antibodies increases gradually reaching its peak at around 10 weeks (third month) and then declines gradually. Conclusion Seropositivity among COVID-19 cases is 62.38%. The proportion of cases with IgG antibodies reaches its peak at around 10 weeks (third month) after diagnosis and then declines gradually. This fall indicates that the detected antibodies may not be long-lasting and may become undetectable/absent over a period of time. The reason for seronegative results in COVID-19 cases needs further in-depth scientific research.

Population-based seropositivity for IgG antibodies against SARS-CoV-2 in Ahmedabad city.

CONTEXT: Ahmedabad city with approximately 7 million population was one of the earliest cities to witness the high case load of COVID-19 pandemic in India. A population-based sero-survey was ideally suited in Ahmedabad to guide the public health response for managing COVID-19 pandemic. OBJECTIVES: To study the percentage sero-positivity for SARS-CoV-2 to understand the pandemic status and deriving conclusions for guiding the public health measures for managing the COVID-19 pandemic. SETTINGS AND DESIGN: Population-based cross-sectional sero-surveillance. METHODS AND MATERIAL: Large scale sero-surveillance with population-based stratified sampling covering more than 10,000 samples from general population of Ahmedabad was carried out during second half of August 2020. The seropositivity was correlated and compared with various demographic factors and other parameters for valid and precise predictions on the immunity status of the population. RESULTS: With 2,396 samples positive for IgG antibodies from a total of 10,310 samples, the seropositivity against COVID-19 in the general population of Ahmedabad is around 23.24%. The seropositivity has increasing trend with increasing age and is significantly higher among females (25.37%) than males (21.81%). The zone wise positivity ranged from 11.74% to 33.14%. This closely correlates with the cases recorded so far, higher for those zones with high current or past cases. CONCLUSIONS: Seropositivity of 23.24% in general population indicate the overall current level of protection. Since effective vaccine is not yet available, it is required to continue emphasis on the public health preventive measures for controlling and managing the COVID-19 pandemic.

Reassessing the population based Seroprevalence for IgG antibodies against SARS COV2 in Ahmedabad

Background: Assessing population based seroprevalence can help in monitor the pandemic, and suggest appropriate corrective public health measures. Aims and Objectives: To study seroprevalence of IgG antibodies against SARS-CoV2 to understand the pandemic status and deriving valid conclusions for guiding the public health measures for managing the covid19 pandemic. Materials and Methods: A serosurveillance study was carried out using population based stratified sampling for the general population of Ahmedabad city. Seroprevalence for Cases, Contacts and Health Care Workers (HCWs) was also estimated as separate additional categories. The seroprevalence was compared with various demographic factors for valid and precise predictions regarding the immunity status of the population. Results: As on October 2020, the seroprevalence for IgG antibodies against SARS-CoV2 in the general population of Ahmedabad is 24.20% (95% Confidence Interval 23.57%–24.85%) The sero-positivity has increasing trend with age and is higher among females (24.83%) than males (23.72%) but is statistically not significant. The zone wise positivity ranged from 18.70% to 33.52%. The seropositivity among HCWs, contacts and cases are 20.84%, 26.05% and 54.51% respectively and it closely correlate with the risk. Conclusion: As on October 2020, general population demonstrate a seropositivity of 24.20%. The seropositivity among various groups is according to the risk of contracting the disease. Results also indicate the possibility of undetectable level or disappearing IgG during the post-covid period. Results also indicate that the preventive measures must be strongly followed for continued control of the pandemic situation till an effective vaccine is provided to the people at large. [ABSTRACT FROM AUTHOR] Copyright of Asian Journal of Medical Sciences is the property of Manipal Colleges of Medical Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

SARS-CoV2 IgG antibody: Seroprevalence among health care workers.

BACKGROUND: Health Care Workers (HCWs) are at higher risk for Covid19. Sero-surveillance among HCWs using IgG antibodies can add further value to the scientific findings. OBJECTIVES: To estimate seropositivity among HCWs and to correlate it with various factors affecting seropositivity. METHODS: Population based large scale sero-surveillance among HCWs was carried out during second half of August'20 in Ahmedabad using "Covid-Kavach" IgG Antibody Detection ELISA kits. Seropositivity among HCWs was estimated and compared with various demographic & other factors to understand their infection & immunity status. Proportions and Z-test were used as appropriate. RESULTS: As on August'20, Seropositivity among HCWs from Ahmedabad is 23.65% (95% Confidence Interval 21.70-25.73%). Seropositivity of 25.98% (95%CI 23.47-28.66) among female HCWs is significantly higher than 19.48% (95%CI 16.53-22.80) among male HCWs. The zone wise positivity among HCWs closely correlate with cases reported from the respective zone. The sero-positivity among HCWs from the earliest and worst affected zones have lower level of seropositivity as compared to the zones affected recently. This might be pointing towards the fact that the IgG Antibodies may not be long lasting. CONCLUSION: As on August 2020, the seropositivity of 23.65% in HCWs indicate high level of disease transmission and higher risk of infection among HCWs in Ahmedabad. The seropositivity is significantly higher among female HCWs. Zone wise seropositivity, closely correlate with the reported cases from the respective zone. Their comparison also indicates the possibility of reducing IgG seropositivity, which necessitates further in-depth scientific research to generate greater scientific evidences.

Severe acute respiratory syndrome coronavirus 2 immunoglobulin G antibody: Seroprevalence among contacts of COVID-19 cases.

BACKGROUND: Multiple serosurveillance studies have focused on the presence of antibodies against severe acute respiratory syndrome coronavirus 2 in the general population and confirmed cases. However, seroprevalence of immunoglobulin G (IgG) among contacts of confirmed cases can add further value to the scientific findings. OBJECTIVES: The objective is to estimate COVID-19 seropositivity among contacts of COVID-19 cases and to compare the seropositivity between types of contact for the assessment of differential risk and transmission dynamics. METHODS: Large scale population-based serosurveillance on contacts of COVID-19 cases was carried out during the second half of August 2020 in Ahmedabad using the COVID-Kavach. The seropositivity among contacts was estimated and correlated-compared with type of contact and other demographic factors. RESULTS: With 1268 positive for IgG antibodies from 3973 samples, the seropositivity against COVID-19 among contacts of cases in Ahmedabad was 31.92% (95% confidence interval 30.48%-33.38%). The seropositivity among family contacts was significantly higher (39.36%) as compared to other contacts (28.72%) (Z = 6.60, P < 0.01). This trend is seen across all age groups and both the sex groups. The seropositivity has increasing trend with increasing age and is significantly higher among females (35.11%) than males (28.95%) (Z = 4.16, P < 0.01). CONCLUSION: Seropositivity of 31.92% among contacts indicates that a large proportion of contacts have already acquired immunity on account of their contact with the case. Higher seropositivity among family contacts justifies the risk categorization and testing strategy adopted for the contacts of the cases. This also reaffirms the need for contact tracing strategy for controlling the inevitable spread of pandemic.

Assessing seropositivity for IgG antibodies against SARS-CoV-2 in Ahmedabad city of India: a cross-sectional study.

OBJECTIVES: To study the percentage seropositivity for SARS-CoV-2 to understand the pandemic status and predict the future situations in Ahmedabad. STUDY DESIGN: Cross-sectional study. SETTINGS: Field area of Ahmedabad Municipal Corporation. PARTICIPANTS: More than 30 000 individuals irrespective of their age, sex, acute/past COVID-19 infection participated in the serosurvey which covered all the 75 Urban Primary Health Centres (UPHCs) across 48 wards and 7 zones of the city. Study also involved healthcare workers (HCWs) from COVID-19/non-COVID-19 hospitals. INTERVENTIONS: Seropositivity of IgG antibodies against SARS-CoV-2 was measured as a mark of COVID-19 infection. PRIMARY AND SECONDARY OUTCOMES: Seropositivity was used to calculate cumulative incidence. Correlation of seropositivity with available demographic detail was used for valid and precise assessment of the pandemic situation. RESULTS: From 30 054 samples, the results were available for 29 891 samples and the crude seropositivity is 17.61%. For all the various age groups, the seropositivity calculated between 15% and 20%. The difference in seropositivity for both the sex group is statistically not significant. The seropositivity is significantly lower (13.64%) for HCWs as compared with non-HCWs (18.71%). Seropositivity shows increasing trend with time. Zone with maximum initial cases has high positivity as compared with other zones. UPHCs with recent rise in cases are leading in seropositivity as compared with earlier and widely affected UPHCs. CONCLUSIONS: The results of serosurveillance suggest that the population of Ahmedabad is still largely susceptible. People still need to follow preventive measures to protect themselves till an effective vaccine is available to the people at large. The data indicate the possibility of vanishing immunity over time and need further research to cross verify with scientific evidences.