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ORIGINAL ARTICLE
Year : 2022  |  Volume : 15  |  Issue : 7  |  Page : 55-59  

Community-Based Cross-Sectional Study of the Relationship between Sars-Cov-2 Antibody Titres and Clinico-Epidemiological Profile of Population above 6 Years of Age in the Pimpri Chinchwad, Pune, Maharashtra


1 Department of Community Medicine, PCMC's Postgraduate Medical Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, Maharashtra, India
2 Department of Pathology, PCMC's Postgraduate Medical Institute and Yashwantrao Chavan Memorial Hospital, Pimpri, Pune, Maharashtra, India
3 Senior Medical Officer, Medical Department, New Thergaon Hospital, Thergaon, Pune, Maharashtra, India

Date of Submission29-Jan-2022
Date of Decision26-Feb-2022
Date of Acceptance15-Apr-2022
Date of Web Publication17-May-2022

Correspondence Address:
Shruti R Gaikwad
301, D2, Mahindra Antheia, Nehru Nagar Road, Pimpri - 411 018, Pune, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mjdrdypu.mjdrdypu_80_22

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  Abstract 


Context: COVID-19 response needs to be enlightened with representative data regarding the humoral response to the virus, and its relationship with the clinico-epidemiological profile of the general population. Aims: To estimate the titres of IgG antibodies against SARS-CoV-2 and study the factors associated with the same among the general population of the Pimpri Chinchwad Municipal Corporation area. Settings and Design: Population-based cross-sectional study was carried out among the general population aged 6 years and above in the Pimpri Chinchwad Municipal Corporation area. Methods and Material: A total of 10,082 individuals from 106 wards of the PCMC area were studied between June 16, 2021 and June 26, 2021. The survey form questionnaire included sociodemographic details, COVID-19 exposure history, symptoms, tests, and vaccination status. About 3 to 5 ml blood samples were collected from each subject. Testing of samples was done using ABBOTT CMIA, SARS-CoV-2 quant assay—sensitivity 92.7% and specificity 99.9%. Statistical Analysis Used: Frequency analysis was done for sociodemographic variables, and antibody titres. An appropriate test of association was applied to the association between antibody titres and the sociodemographic and clinical profile of participants. Results: Antibody titres were significantly higher in males, aged 45 years and above, participants of upper socioeconomic class, participants residing in elite areas, subjects with a history of COVID-like symptoms in the past, and those who were vaccinated. Conclusions: Anti-SARS-CoV-2 IgG antibodies titres were found to be significantly associated with age, sex, socioeconomic status, area of residence, vaccination status, and history of COVID symptoms.

Keywords: Antibody titre, COVID-19, Pimpri Chinchwad, Pune, serosurvey


How to cite this article:
Pandve HT, Bawa MS, Desale AV, Gaikwad SR, Patil T, Dadewar AA. Community-Based Cross-Sectional Study of the Relationship between Sars-Cov-2 Antibody Titres and Clinico-Epidemiological Profile of Population above 6 Years of Age in the Pimpri Chinchwad, Pune, Maharashtra. Med J DY Patil Vidyapeeth 2022;15, Suppl S1:55-9

How to cite this URL:
Pandve HT, Bawa MS, Desale AV, Gaikwad SR, Patil T, Dadewar AA. Community-Based Cross-Sectional Study of the Relationship between Sars-Cov-2 Antibody Titres and Clinico-Epidemiological Profile of Population above 6 Years of Age in the Pimpri Chinchwad, Pune, Maharashtra. Med J DY Patil Vidyapeeth [serial online] 2022 [cited 2022 Sep 28];15, Suppl S1:55-9. Available from: https://www.mjdrdypv.org/text.asp?2022/15/7/55/345406




  Introduction Top


On January 30, 2020, the Director-General declared the novel coronavirus outbreak a public health emergency of international concern (PHEIC), WHO's highest level of alarm.[1] WHO announced the COVID-19 outbreak as a pandemic on March 11, 2020.[2] As of December 26, 2020, over 278 million cases and just under 5.4 million COVID deaths have been reported globally.[3] Approximately 1 in 15 individuals aged 10 years or older in India had SARS-CoV-2 infection by August 18, 2020.[4]

Serology or antibody testing checks a sample of a person's blood to look for antibodies against SARS-CoV-2, the virus that causes COVID-19. Nearly, all immunocompetent persons develop an adaptive immune response following SARS-CoV-2 infection, including B and T cell-mediated immunity[5],[6],[7] due to antiviral humoral and cellular immune responses, respectively. Our understanding of the immune response to SARS-CoV-2 is rapidly advancing. Persons with more severe diseases appear to develop a more robust antibody response with IgM, IgG, and IgA, all achieving higher titres and exhibiting longer persistence.[8],[9] India's fourth “serosurvey” of the COVID pandemic has found neutralizing antibodies to the novel coronavirus in 67.6% of people aged over 6 years, suggesting that more than two in three people have already been exposed to the virus or a vaccine.[10] Usually, antibody tests can be used for disease detection after 5 to 7 days of illness. IgM antibodies are evident in the blood for the first 2 months and IgG antibodies generally start appearing after 2 weeks of the onset of infection and last for several months.[10],[11],[12] Thus, although these tests are not useful for detecting acute infection, population-based seroepidemiological studies could be useful to understand the cumulative exposure levels to the infection and make inferences on the actual burden of infection, its geographical spread, effect on specific demographic/risk groups, gaps in testing, and infection fatality rates.[13],[14] The information from such studies will also help monitor the extent of the ongoing immunization programs as vaccination drives are already started in different countries including India.[15]

Pimpri Chinchwad is a metropolitan city and had an overall positivity rate of 12.90%, in comparison to Maharashtra state's overall positivity rate which stands at 10.55%, while that of India is at 5.33%.[16] There is evidence that neutralizing antibodies have a positive correlation with age, male sex, and severity of the disease; however, COVID-19 response urgently needs to be enlightened with more representative data and, in particular, regarding the humoral response to the virus, and its relationship with the clinico-epidemiological profile of the general population. This study was conducted to estimate the titres of IgG antibodies against SARS-CoV-2, and study the factors associated with the same among the general population of the Pimpri Chinchwad Municipal Corporation area.


  Subjects and Methods Top


A population-based cross-sectional study was carried out among the general population aged 6 years and above in the Pimpri Chinchwad Municipal Corporation area between June 16, 2021, and June 26, 2021. As per a previous serosurvey carried out in PCMC in October 2020, the seroprevalence rate of SARS-CoV-2 IgG antibodies was 34.04%,[17] with a precision of 0.1% and 99% confidence interval, and a design effect of 2.5% sample size calculated was 9687 which was rounded to 10,000. Individuals, aged above 6 years, who were identified for recruitment into the investigation were included in the study. Those who refused to participate or had contraindication for venepuncture were excluded. Further, the participants eligible after exclusion were selected using stratified cluster random sampling. The negative response rate in the study was negligible.

The PCMC area was divided into 106 administrative wards. The area was stratified into slum and non-slum areas. PCMC also caters to approximately 7 lakh population who live in close houses with no or minimal space between them. Although they differ marginally in their housing structures, they were broadly referred to as “Chawl-like settlements” or Gaothan during the study. Hence, non-slum areas were further stratified into Gaothan and elite areas.

Probability proportionate to size sampling was done to calculate sample size for each of these strata as per the 2011 census. Clusters were selected from the cumulative sample from each stratum. The household was considered as a sampling unit and samples were taken from all the individuals in a house. A total of 200 clusters with 50 samples from each cluster of three strata based on the housing structure such as slum, tenements (Gaothan), and housing societies (elite) with 35, 45, and 120 clusters each, respectively, were selected.

The stratum was further divided into four quadrants based on the number of clusters: North-East, North-West, South-East, and South-West. The first house of the cluster was then randomly selected from the quadrant. In a cluster, every fourth house was selected from the first house. If the house was closed or nonresponsive, the next house was taken until the required number of households was met. For elite areas with apartments, one house was selected randomly from every fourth apartment.

The survey form questionnaire included sociodemographic data of the subject, the COVID-19 exposure history, symptoms in case of confirmed/suspected COVID-19, details of COVID-19 tests done, and COVID-19 vaccination status. The questionnaire was administered by the trained Medical officers/ANM. Blood samples were collected by trained lab technicians; 3 to 5 ml blood samples were collected from each subject. The serum is separated from these blood samples by centrifugation. Testing of samples was done using ABBOTT CMIA, SARS-CoV-2 quant assay—sensitivity is 92.7% and specificity is 99.9%. Serum samples were stored in a -200°C deep freezer for 6 months.

Ethical approval was taken from the institutional ethics committee PCMC's PGI and YCMH Pimpri. Informed consent was obtained from all individuals willing to participate in the investigation. For children under the legal age, assent was obtained from a parent or legal guardian. The obtained data were entered into a MS-Excel worksheet. Frequency analysis was done for sociodemographic variables and antibody titres. An appropriate test of association was applied to the association between antibody titres and the sociodemographic and clinical profile of participants.


  Results Top


Out of the total 10,082 population surveyed, 6299 (62.5%) were living in the elite area followed by the tenements area (23%) and slum (14.5%). Gender wise, females were 5236 (52%) and males were 4846 (48%). Age wise, 8452 (84%) surveyed were above 18 years of age, also we had surveyed 1630 (16%) population from 6 to 18 years of age.

Religion wise, 89% population surveyed was Hindu followed by Buddhist (3.5%); 93% population surveyed were literate and only 7% were illiterate. When we assessed socioeconomic status by the modified Kuppuswamy scale, 3675 (37%) subjects belonged to upper lower SES, although 25% of participants did not give adequate information to decide on their SES. The overall seroprevalence of SARS-CoV-2 IgG antibodies was 81.34% in this study.

[Table 1] shows the association of various factors with IgG titres against SARS-CoV-2. Median antibody titres were highest in the elite area (927 IU). There was a significant difference observed in the antibody titres between the elite and slum areas. The age group above 45 years showed significantly higher antibody titres than age below 45 years. Male participants had slightly higher antibody titres as compared with females which were statistically significant. Upper SES had a median titre of 1180 IU which was the highest. Also, there was a significant difference in median titre between upper and lower SES. Those who had symptoms suggestive of COVID-19 in the past had median titre of 1947 IU which is significantly higher than the asymptomatic (800 IU). Participants taking at least one dose of the COVID vaccine had at least 5-fold more median antibody titre, which was statistically significant. Participants below 18 years of age were not eligible for vaccination, and 1630 such participants were also included in the non-vaccinated group. There was no significant difference in the median titres of those who had taken one dose of the vaccine as compared to those who had taken both doses.
Table 1: Association of various factors with IgG titres against SARS-CoV-2

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  Discussion Top


India remains the second country after the USA which is most severely impacted by the COVID-19 pandemic. Population-based seroepidemiological studies probe the extent of the population that has antibodies against SARS-CoV-2, either due to exposure to natural infection or post-vaccination. A lot of research regarding the immune response to the virus revolves around inpatients and healthcare workers and the results of the same cannot be extrapolated to the general population.

This study was conducted to estimate the titres of IgG antibodies against SARS-CoV-2 and study the factors associated with the same among the general population of the Pimpri Chinchwad Municipal Corporation area. A serosurvey was conducted among 10,082 individuals aged 6 years and above in the Pimpri Chinchwad Municipal Corporation area. The age group above 45 years showed significantly higher antibody titres than age below 45 years. Bag Soytas R, Cengiz M, Islamoglu MS, et al.[18] in a study, comparing COVID-19 IgG Ab levels in young and older adults, found IgG Ab titres to SARS-CoV-2 to be meaningfully higher in older adults and that, there was a positive correlation between age and Ab titres. Tretyn A et.al[19] evaluated the titre of anti-SARS-CoV-2 IgG antibodies in 477 adult volunteers in Toruń, Poland, and discovered a noticeable trend that was the higher concentration values for people aged 36 to 45 and 46 to 55 years. Wu et al.[20] reported that NAbs were higher among older patients compared to those middle-aged and younger, the latter being those with lower neutralizing titres. We found that the antibody titres were significantly higher in men as compared to women. Wang X, Guo X, Xin Q, Pan Y, Hu Y, Li J, et al.,[21] Klein SL, Pekosz A, Park HS, Ursin RL, Shapiro JR, Benner SE, et al.,[22] and Jin JM, Bai P, He W, Wu F, Liu XF, Han DM, et al.[23] concluded that there are significant differences in the course and outcome of the disease between men and women, and worse outcomes and higher antibody titres among the male population.

Those who had symptoms suggestive of COVID-19 in the past had median titre of 1947 IU which is significantly higher than the asymptomatic (800 IU). Perhaps one of the clearest and most well-understood topics regarding antibody kinetics is the relationship with severity. Several reports, including systematic reviews, opinion articles, and original articles, point toward this same conclusion, strongly asserting that severity in COVID-19 patients seems to be associated with antibody production and response against this virus.[24],[25],[26],[27] Long QX, Tang XJ, Shi QL, Li Q, Deng HJ, Yuan J, et al.[28] in their study found that virus-specific IgG levels in the asymptomatic group were significantly lower relative to the symptomatic group.

The 106 wards of area of PCMC were stratified into slum and non-slum areas, and non-slum areas were further stratified into Gaothan and elite areas. Several serosurveys conducted across the nation have reported higher seropositivity in slum areas compared to the non-slum areas.[29],[30],[31] However, we compared the titres of IgG antibodies against SARS-CoV-2 in elite versus slum areas and found significantly higher titres in the former. We found that participants taken at least one dose of the COVID vaccine had at least 5-fold more median antibody titre than those not vaccinated.

This study has conducted a population-based cross-sectional study which was carried out among the general population aged 6 years and above in 106 wards of the Pimpri Chinchwad Municipal Corporation including the slum and non-slum areas to estimate the titres of IgG antibodies against SARS-CoV-2 and study the factors associated with the same. There are certain limitations to this study. The study being cross-sectional in nature does not probe into the kinetics of IgG antibodies against SARS-CoV-2. Also, the study does not probe into cellular immunity, which provides protective and long-lasting immunity against the virus.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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