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Journal ArticleDOI

SARS-CoV-2 Antibody Prevalence in India: Findings from the Second Nationwide Household Serosurvey, August - September 2020

TL;DR: Seroprevalence was highest in urban slum areas followed by urban non-slum and rural areas and a cumulative 74·3 million infections in the country, with 26 – 32 infections for every reported COVID-19 case by August 2020.
Abstract: Background: The first round of national serosurvey in India was conducted in May-June 2020 among adults from 21 States. The second serosurvey was conducted in August-September 2020 to estimate the nationwide seroprevalence for SARS-CoV-2 infection in the general population aged ten years and above. Methods: The household serosurvey was conducted among individuals aged ten years and above in the same 700 villages and wards from 70 districts selected during the first serosurvey. Blood samples were tested using the Abbott SARS-CoV-2 IgG assay. Seroprevalence was estimated after applying the sampling weights and adjusting for clustering and assay characteristics. In order to compare the adult seroprevalence between the two surveys, we randomly selected one adult serum sample from each household. Findings: The weighted and adjusted prevalence of infection among 29,082 individuals aged ten years and above was 6·6% (95% CI: 5·8% - 7·4%). The seroprevalence among adults was 7·1% (95% CI: 6·2% – 8·2%). Seroprevalence was similar across age groups, sex, and occupation. Seroprevalence was highest in urban slum areas followed by urban non-slum and rural areas. We estimated a cumulative 74·3 million infections in the country, with 26 – 32 infections for every reported COVID-19 case by August 2020. Interpretation: Nearly one in 15 individuals aged ten years and above had SARS-CoV-2 infection by August 2020. The adult seroprevalence increased ten times between May and August 2020. Lower infection to case ratio in August compared to May reflects a substantial increase in testing across the country. Funding: The study was funded by the Indian Council of Medical Research, New Delhi, India. The study sponsor was involved in reviewing the study design, writing of the manuscript and the decision to submit the paper for publication. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: The authors obtained written informed consent from individuals aged 18 years and older. We obtained assent from children aged between 10–17 years, and written informed consent from their parents or guardians prior to the survey. The Central Ethics Committee of Health Research of Indian Council of Medical Research and the Institutional Human Ethics Committee of ICMR-National Institute of Epidemiology, Chennai approved the study protocol.
Citations
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Journal ArticleDOI
TL;DR: In this article, a systematic review and meta-analysis of serological surveys for antibodies to SARS-CoV-2 have been reported worldwide, and the authors aimed to synthesise, combine, and assess this large corpus of data.

174 citations

Posted ContentDOI
14 Dec 2020-medRxiv
TL;DR: Despite high IgG seroprevalence, there was evidence for waning of antibody positivity with the progression of the COVID-19 epidemic, implying a potential reduction in population immunity, especially if also associated with the lack of trained T cell immunity.
Abstract: Background Three rounds of a repeated cross-sectional serosurvey to estimate the seroprevalence and trends of SARS-CoV-2 were conducted from August-October’ 2020 in the state of Delhi in India in the general population aged ≥5 years. Methods The selection of participants was through a multi-stage sampling design from all the 11 districts and 280 wards of the city-state, with two-stage allocation proportional to population- size. Household selected was via systematic random sampling, and individual participant selection through the age-order procedure. The blood samples were screened using the IgG ELISA COVID-Kawach kit (August Round), and the ERBALISA COVID-19 IgG (September and October) rounds. The seroprevalence was estimated by applying the sampling weights based on age and sex with further adjustment for the assay-kit characteristics. Results A total of 4267 (n=15046), 4311 (n=17409), and 3829 (n=15015) positive tests indicative of the presence of IgG antibody to SARS-CoV-2 were observed during the August, September, and October 2020 serosurvey rounds, respectively. The adjusted seroprevalence declined from 28.39% (95% CI 27.65-29.14) (August) to 24.08% (95% CI 23.43-24.74) (September), and 24.71% (95% CI 24.01, 25.42%) (October). The antibody positivity was highest in the ≥50 and female age-group during all rounds of the serosurvey, while the decline was maximum among the younger age-group (5-17 years). On adjusted analysis, participants with lower per capita income, living in slums or overcrowded households, and those with diabetes comorbidity had significantly higher statistical odds of antibody positivity. Conclusions Despite high IgG seroprevalence, there was evidence for waning of antibody positivity with the progression of the COVID-19 epidemic, implying a potential reduction in population immunity, especially if also associated with the lack of trained T cell immunity.

31 citations

Posted ContentDOI
TL;DR: In this article, a simple mathematical model with a flexible transmission rate was proposed to reconstruct the transmission rate, estimate the infection fatality rate and forecast the epidemic size in COVID-19 pandemic in India.
Abstract: By February 2021, the overall impact of the COVID-19 pandemic in India had been relatively mild in terms of total reported cases and deaths. Surprisingly, the second wave in early April becomes devastating and attracts worldwide attention. Multiple factors (e.g., Delta variants with increased transmissibility) could have driven the rapid growth of the epidemic in India and led to a large number of deaths within a short period. We aim to reconstruct the transmission rate, estimate the infection fatality rate and forecast the epidemic size. We download the reported COVID-19 mortality data in India and formulate a simple mathematical model with a flexible transmission rate. We use iterated filtering to fit our model to deaths data. We forecast the infection attack rate in a month ahead. Our model simulation matched the reported deaths well and is reasonably close to the results of the serological study. We forecast that the infection attack rate (IAR) could have reached 43% by July 24, 2021, under the current trend. Our estimated infection fatality rate is about 0.07%. Under the current trend, the IAR will likely reach a level of 43% by July 24, 2021. Our estimated infection fatality rate appears unusually low, which could be due to a low case to infection ratio reported in previous study. Our approach is readily applicable in other countries and with other types of data (e.g., excess deaths).

16 citations

Journal ArticleDOI
02 Jul 2021-BMJ Open
TL;DR: In this article, the authors investigated the impact of targeted vaccination strategies on morbidity and mortality due to COVID-19, as well as on the incidence of SARS-CoV-2, in India.
Abstract: Objectives To investigate the impact of targeted vaccination strategies on morbidity and mortality due to COVID-19, as well as on the incidence of SARS-CoV-2, in India. Design Mathematical modelling. Settings Indian epidemic of COVID-19 and vulnerable population. Data sources Country-specific and age-segregated pattern of social contact, case fatality rate and demographic data obtained from peer-reviewed literature and public domain. Model An age-structured dynamical model describing SARS-CoV-2 transmission in India incorporating uncertainty in natural history parameters was constructed. Interventions Comparison of different vaccine strategies by targeting priority groups such as keyworkers including healthcare professionals, individuals with comorbidities (24–60 years old) and all above 60. Main outcome measures Incidence reduction and averted deaths in different scenarios, assuming that the current restrictions are fully lifted as vaccination is implemented. Results The priority groups together account for about 18% of India’s population. An infection-preventing vaccine with 60% efficacy covering all these groups would reduce peak symptomatic incidence by 20.6% (95% uncertainty intervals (UI) 16.7–25.4) and cumulative mortality by 29.7% (95% CrI 25.8–33.8). A similar vaccine with ability to prevent symptoms (but not infection) will reduce peak incidence of symptomatic cases by 10.4% (95% CrI 8.4–13.0) and cumulative mortality by 32.9% (95% CrI 28.6–37.3). In the event of insufficient vaccine supply to cover all priority groups, model projections suggest that after keyworkers, vaccine strategy should prioritise all who are >60 and subsequently individuals with comorbidities. In settings with weakest transmission, such as sparsely populated rural areas, those with comorbidities should be prioritised after keyworkers. Conclusions An appropriately targeted vaccination strategy would witness substantial mitigation of impact of COVID-19 in a country like India with wide heterogeneity. ‘Smart vaccination’, based on public health considerations, rather than mass vaccination, appears prudent.

10 citations

Journal ArticleDOI
TL;DR: A serosurvey prior to initiation of the vaccination program to understand the extent of the SARS-CoV-2 outbreak was carried out in Sri Lanka as mentioned in this paper, where the overall seropositivity rate was 24.46%.
Abstract: Background As the Municipality Council area in Colombo (CMC) experienced the highest number of cases until the end of January 2021, in Sri Lanka, we carried out a serosurvey prior to initiation of the vaccination program to understand the extent of the SARS-CoV-2 outbreak. Methods SARS-CoV-2 seropositivity was determined in 2547 individuals between the ages of 10 to 86 years, by the Wantai total antibody ELISA. We also compared seroprevalence using the haemagglutination test (HAT) to evaluate its usefulness in carrying out serosurveys. Results The overall seropositivity rate was 24.46%, while seropositivity by HAT was 18.90%. Although The SARS-CoV-2 infection detection rates by PCR were highest in the population between the ages of 20 to 60 years of age, there was no statistically significant difference in the seropositivity rates in different age groups. For instance, although the seropositivity rate was highest in the 10 to 20 age group (34.03%), the PCR positivity rate was 9.80%. Differences in the PCR positivity rates and seropositivity rates were also seen in 60 to 70-year-olds (8.90% vs 30.4%) and in individuals >70 years (4.10% vs 1.20%). The seropositivity rate of the females was 29.70% (290/976), which was significantly higher (p<0.002) than in males 21.2% (333/1571). Conclusions A high seroprevalence rate (24.5%) was seen in all age groups in the CMC suggesting that a high level of transmission was seen during this time. The higher PCR positivity rates between the ages of 20-60 is likely to be due to increased testing carried out in the working population. Therefore, the PCR positivity rates, appear to underestimate the true extent of the outbreak and the age groups which were infected.

8 citations

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