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Background: This study was conducted to understand the transmission dynamics of COVID-19 virus among the household contacts of RT-PCR confirmed cases to have an insight on key epidemiological characteristics of the infection. Methods: This was a prospective case-ascertained study conducted among the contacts of laboratory-confirmed COVID-19 cases residing in the same household in the Central and North-East districts of Delhi between 28th December 2020, and 28th June 2021. Data and specimen for reverse transcription polymerase chain reaction (RT-PCR) and serology were collected from the primary case and their contacts on day one of the visit, and follow-up collection of data and specimen was done on day 7, 14 and 28. A daily symptom diary was also maintained for all the primary cases and their contacts till 28 days from enrolment in the study. A total of 109 houses were enrolled in the study. Results: The secondary attack rate (SAR) estimated among the household contacts was 13.86% [95% C.I. 9.71%, 19.39%] and the secondary infection rate was 33.16% [95% C.I. 26.97%, 40.00%]. The serial interval and basic reproduction number (R0) within the household were estimated to be 3.6± 5.73 days and 1.26 [95% C.I. 1.21—1.31], respectively. Significant predictors of the infection were location of household in central district (SAR = 20% [13.75, 28.16]) versus North-East District (SAR = 4.87% [1.83-12.35]) p= 0.002, sharing of utensils (SAR= 42.85% [14.26—77.11], p=0.02), and using the room to sleep where a specific case has been isolated (SAR= 25% [12.97—42.71], p=0.047). Transmission from the symptomatic primary case was observed to be five times higher. Conclusion: Our analysis showed that the secondary infection rate was higher among household contacts. This study suggests a dose-response association between severity of the primary case of SARS CoV-2 and infection among contacts.

Background: In India, laboratory diagnosis of SARS – CoV-2 infection has been mostly based on real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Studies have shown that Viral titres peak within the first week of symptoms but may decline later hampering RT-PCR-based diagnostic strategies. Exact estimate is difficult under high-risk screening strategy with evidences of having large number of asymptomatic cases. This has prompted a call for adoption of antibody testing as potential source of data. Materials and Methods: A cross-sectional study with a sample size of 7000 was conducted for 15 days including all the 85 wards under Indore Municipal Corporation. Stratified Random Sampling was used to collect the samples. Trained teams collected basic sociodemographic information and serum samples which were tested for the presence of specific antibodies to COVID-19 using ICMR-Kavach IgG ELISA kits. The data collected was compiled and analysed using appropriate statistical software. Results: Overall weighted seroprevalence of the study population was found to be 7.75%. The prevalence in males and females was comparable (7.91% vs 7.57%). Highest seropositivity (10.04%) was seen among individuals aged more than 60 years. Total number of infections in the population were estimated to be 2,03,160. Overall Case Infection Ratio was found to be 27.43. Conclusion: The current seroprevalence study provides information on proportion of the population exposed, but the correlation between presence and absence of antibodies is not a marker of total or partial immunity. It must also be noted that more than 90 percent of the population is still susceptible for COVID-19 infection. Hence, non-pharmaceutical interventions like respiratory hygiene, physical distancing, hand sanitization, usage of personal protective equipment such as masks and implementation of public health measures need to be continued.

Background: Non-Pharmacological Interventions (NPIs) have proven to be effective in controlling and reducing the spread of SARS-CoV-2 in the population. During the year 2020, before vaccine introduction, India has been through various phases of COVID-19 pandemic response such as nationwide lockdown phase 1 to 4 and unlock phases 1-8. Although India’s vaccination program against COVID-19 has started, it is still in the initial phases and considering the humongous population of India, coverage of entire population with vaccine needs time. Methodology: We designed a model showing the projections of expected incident cases of COVID-19 under two scenarios for the month of February 2021. In the first scenario, Rt value expected to be observed during February 2021 if all the NPIs are removed was considered. In the second scenario, Rt value projected as per the current trend with NPIs in place was considered. Model projections of both these scenarios were done for India and also for Delhi. Result: Our simulation model quantifies the effect of Non-pharmacological interventions on the current pandemic situation in India and Delhi, which concludes that relaxation in preventive measures or COVID-19 appropriate behaviors or ceasing of NPIs shall see an exponential rise in the daily incident cases. Comparing the trajectories for India and Delhi, it can be deduced that if NPIs cease to exist for one month, the daily incident cases can be many times higher of normal in India and also in Delhi by the end of February 2021. Conclusion: NPIs remain to play a major role in containing the spread and minimizing the effects of COVID-19 pandemic. Any kind of relaxation in NPIs can lead to sudden surge of incident cases and correspondingly may increase the death toll.

Antibody test is used in seroprevalence surveys for Coronavirus Disease-2019 (COVID-19). Apart from estimating the proportion of population infected, they can help in drawing plenty of inferences about the extent, progress and course of the pandemic. They can potentially be helpful in planning and prioritising vaccine distribution by providing a broad overview into proportion of population immune to COVID-19 in a geographic area and also help in understanding the pockets of high or low seroprevalence. This review was conducted with an aim of compiling an updated and comprehensive information about the seroprevalence of the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) antibody in various pockets of India in the year 2020, and thus to understand the current pandemic situation in the country. A total of 35 studies were identified through all resources and detailed review was carried out based on these studies. Additionally, indicators were devised to understand and compare the results. Results were further classified into states/Union Territories (UTs), districts, Sub-district regions. The study findings show that the anti SARS-CoV-2 antibodies seroprevalence estimates vary across different regions (states/UTs, districts, sub district regions) of India and can increase or in some instances decrease over the course of time. The study concludes by asserting the need for repeated seroprevalence surveys as well as follow-up studies for current pandemic surveillance.