key: cord-0954242-9pmy6lq4 authors: Prakash, Om; Solanki, Bhavin; Sheth, Jay; Makwana, Govind; Kadam, Mina; Vyas, Sheetal; Shukla, Aparajita; Pethani, Jayshri; Tiwari, Hemant title: SARS-CoV2 IgG antibody: Seroprevalence among health care workers date: 2021-05-08 journal: Clin Epidemiol Glob Health DOI: 10.1016/j.cegh.2021.100766 sha: 8b2d2042b7000c708c03728d9d877206d2144c87 doc_id: 954242 cord_uid: 9pmy6lq4 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. "HCWs" component of the sero-surveillance. Keeping estimation of seroprevalence among HCWs as our primary objective, we also checked the correlation of seropositivity with various demographic and other factors affecting their immunity. Indian Council of Medical Research (ICMR) had issued directives for conducting IgG Antibody based ELISA test for sero-surveys to monitor the pandemic, understand its progression and to take appropriate corrective public health measures. Ahmedabad Municipal Corporation (AMC), from the state of Gujarat, INDIA, planned and conducted a sero-survey using population based stratified sampling during second half of August 2020. Result of the earlier sero-survey in general population of Ahmedabad was used for the purpose of calculating the sample size for the present study. Ward / Urban Primary Health Centre (UPHC) wise required minimum sample size for the general population category was determined based on population proportion with 95% confidence level with 1% margin of error. Along with the general population category, HCWs were also enrolled separately as an additional category along with cases and contact of cases. The sample size for the "HCWs" category was decided as atleast 10% of general population sample target. This sample size was calculated for each ward/UPHC, and thus, the sample size for HCWs was also based on population proportion. The study was carried out after the approval of ethics committee of AMC MET Medical College. Written informed consent was taken for the purpose of the study from all the participants before enrollment. Strict confidentiality was ensured at all levels. For the purpose of testing and standardization, only those laboratories with national level accreditation and state of the art facilities and equipment were approved for testing the samples. To reduce the sample rejection rate, SST-Gel Vacutee were used for the collection of blood samples. Microsoft Excel and Epi-Info was used for the purpose of data management. The crude positivity in HCWs was considered as an indicator for the current level of immunity among field level HCWs. In-depth analysis of the data was carried out with focus on comparing seropositivity among HCWs with various demographic and other factors. Simple proportions and appropriate statistical tests were used wherever required. In this article, we have tried to focus only on the analysis of seroprevalence among HCWs. The comparison of seroprevalence among HCWs with the seroprevalence among general population and other categories have been addressed in other articles and not discussed at stretch in the present study. We herewith share the findings of our results for the detailed insight by the scientific community. We have collected limited demographic details of the enrolled HCWs so that only limited analysis on serosurveillance result was possible. The limitations of the testing kit "Covid-Kavach" automatically applies to the findings of our study. The age distribution of the HCWs typically follows age-heaping bias (data not shown, only grouped data shown in Table- the extremes of the age groups, i.e. 10-19 and 60-69 years age groups. In both these age groups, the sample size is comparatively low. Moreover, health authorities at Ahmedabad have advised low risk work assignment to the 50+ age groups particularly those HCWs with any of the known comorbid condition. So, in the HCWS with 50+ age, there was reduced occupational exposure as compared to other HCWs, atleast in the public health sector. Even in the private health care sector, during the early months of the pandemic, elderly health care workers particularly with comorbidity were avoiding practice and direct clinical exposure. All the above details could possibly explain the low seropositivity in the extremes of the age groups, from whatever little sample that we have enrolled. Seropositivity level is seen on higher side in the age groups representing young adults and middle aged HCWs. This may be related to their field work duty assigned to the health care workers in the public health sector. Even in the private sector, the young aged HCWs were more active in health care services and thus more at risk of having a contact and more likely to develop antibodies against SARS-CoV2 which reflected as seropositivity in the serosurveillance. While checking the trend of seropositivity with a linear trendline, it shows increasing seropositivity with increasing age group among HCWs. We noted that the scientific research studies have documented that young adults are more likely to be asymptomatic, have milder symptoms and for shorter duration, if at all, as compared to the elderly people. (18) (19) (20) (21) It is also documented that percent seroconversion in asymptomatic cases is low. (22) This phenomenon holds true not only for general population but also for HCWs and this may be the reason for higher sero-conversion among middle aged as compared to the young adults. When the same comparison of age-group and sero-positivity is done for both the sex groups ( Figure 2 ) it shows that female HCWs have higher seropositivity for most of the age groups. The linear trendline when plotted for both the sex groups shows that female HCWs have decreasing seropositivity as the age group increases. On the other hand, male HCWs have increasing seropositivity with increase in the age group. This is a typical finding and in the absence of other details for the enrolled HCWs (designation, work setting or affiliations), we can only suggest that a further in-depth scientific study is required to find out the reasons for this difference. This might be pointing towards the fact that the IgG Antibodies may not be long lasting. Scientific studies have also documented declining level of antibodies, which vanishes over a period of time. (25) (26) (27) This needs further research to cross verify with scientific evidences to prove this observation. As on August 2020, the seropositivity of 23. indebted to all the participants whose willingness and support has generated the much-desired data for the study. 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