High seroprevalence of anti-SARS-CoV-2 antibodies in the capital of Chad

Background. Since the start of the COVID-19 pandemic, Chad has had 7,417 confirmed cases and 193 deaths, one of the lowest in Africa. Objective. This study assessed SARS-CoV-2 immunity in N'Djamena. Methods. In August-October 2021, eleven N'Djamena hospitals collected outpatient data and samples. IgG antibodies against SARSCoV- 2 nucleocapsid protein were identified using ELISA. "Bambino Gesu" Laboratory, Rome, Italy, performed external quality control with chemiluminescence assay. Results. 25-34-year-old (35.2%) made up the largest age group at 31.9 12.6 years. 56.4% were women, 1.3 women/men. The 7th district had 22.5% and the 1st 22.3%. Housewives and students dominated. Overall seroprevalence was 69.5% (95% CI: 67.7-71.3), females 68.2% (65.8-70.5) and males 71.2% (68.6-73.8). >44-year-old had 73.9% seroprevalence. Under-15s were 57.4% positive. Housewives (70.9%), civil servants (71.5%), and health workers (9.7%) had the highest antibody positivity. N'Djamena's 9th district had 73.1% optimism and the 3rd district had 52.5%. Seroprevalences were highest at Good Samaritan Hospital (75.4%) and National General Referral Hospital (74.7%). Conclusion. Our findings indicate a high circulation of SARS-CoV- 2 in N'Djamena, despite low mortality and morbidity after the first two COVID-19 pandemic waves. This high seroprevalence must be considered in Chad's vaccine policy.

Clinical and epidemiologic features of SARS-CoV-2 in dogs and cats compiled through national surveillance in the United States

OBJECTIVE: To characterize clinical and epidemiologic features of SARS-CoV-2 in companion animals detected through both passive and active surveillance in the US. ANIMALS: 204 companion animals (109 cats, 95 dogs) across 33 states with confirmed SARS-CoV-2 infections between March 2020 and December 2021. PROCEDURES: Public health officials, animal health officials, and academic researchers investigating zoonotic SARS-CoV-2 transmission events reported clinical, laboratory, and epidemiologic information through a standardized One Health surveillance process developed by the CDC and partners. RESULTS: Among dogs and cats identified through passive surveillance, 94% (n = 87) had reported exposure to a person with COVlD-19 before infection. Clinical signs of illness were present in 74% of pets identified through passive surveillance and 27% of pets identified through active surveillance. Duration of illness in pets averaged 15 days in cats and 12 days in dogs. The average time between human and pet onset of illness was 10 days. Viral nucleic acid was first detected at 3 days after exposure in both cats and dogs. Antibodies were detected starting 5 days after exposure, and titers were highest at 9 days in cats and 14 days in dogs. CLINICAL RELEVANCE: Results of the present study supported that cats and dogs primarily become infected with SARS-CoV-2 following expo- sure to a person with COVID-19, most often their owners. Case investigation and surveillance that include both people and animals are necessary to understand transmission dynamics and viral evolution of zoonotic diseases like SARS-CoV-2.

Seroprevalence of anti-SARS-CoV-2 antibodies in high-risk occupational and low-risk groups in southwestern Iran

Background: Monitoring the spread of SARS-CoV-2 has been considered by the World Health Organization (WHO). We examined the prevalence of anti-SARS-CoV-2 immunoglobulin antibodies in southwestern Iran in spring 2020. The circulation of SARS-CoV-2 is high in the general population, especially among health care workers (HCWs) who are in close contact with patients. Objectives: The aim of this study was to determine the prevalence of anti-SARS-CoV-2 antigen in high-risk occupational and low-risk groups to investigate risk factors for serum positivity in Shiraz, southwestern Iran. Methods: A cross-sectional survey was performed on 366 participants (204 from high-risk and 162 from low-risk subjects). IgG and IgM antibodies were detected using Pishtaz Teb COVID-19 ELISA Kits to evaluate SARS-CoV-2-antigen in serum samples. After enzyme-linked immunosorbent assay (ELISA), serum prevalence, as well as IgG/IgM positive factors, was determined using logistic regression. Results: From July to September 2020 (a few months after reporting the first case of COVID-19 cases in Iran), out of 366 survived people, 72 (40.9%) were IgG positive, and 50 (27.5%) were IgM positive. The frequency of positive serology for IgG and IgM antibodies in individuals aged < 30 years was higher in the low-risk group than in the high-risk group. Multivariate logistic regression showed that headache (OR 0.312 [95% CI: 0.136 - 0.717]) and cough (OR 0.427 [95% CI: 0.182 - 1.004]) factors were associated with IgG or IgM positive serology. Conclusions: Between July and September 2020, the prevalence of anti-SARS-CoV-2 antigen was high in Shiraz. The prevalence of SARS-CoV-2 IgG/IgM antibodies in the high-risk group and their family as low risk was shown to increase viral infection due to close contact with COVID 19 patients than in the general population. Several factors were found to be related to the prevalence of anti-SARS-CoV-2 antigen that needs to be considered by policymakers to determine what to do about the SARS-CoV-2 pandemic.

Seroprevalence and cumulative incidence of COVID-19 in Ravansar cohort study participants 2020: a cross-sectional study

Background and Objectives: Serological studies are based on the detection of antibodies. However, the produced antibodies decrease over time;therefore, such methods cannot provide a valid estimate of prevalence and incidence. The present study aimed to determine the serum prevalence and cumulative incidence in the Ravansar cohort population (Youth and RaNCD Cohort) in October 2020. Methods: A random sample of 716 people aged > 18 years old were selected from the participants in the Ravansar cohort study in October 2020. Euroimmun anti-SARS COV-2 IgG ELISA kits (Lubeck, Germany) were used to measure antibody levels. Seroprevalence was estimated with considering of cut-off = 1, and cumulative incidence (modified and modified based on test specificity) was determined using modeling. Results: In the present study, the serum prevalence of COVID-19 viral infection in the Ravansar cohort population from 22 October 2020 to 18 November 2020 was estimated to be %35.16 (95%CI: %31.64, %38.79). Modified Cumulative incidence and modified based on test characteristics from 20 February to 18 November 2020 were estimated to be %68.85 and %67.71, respectively. Conclusion: Although very high cumulative incidence may be a sign of approaching herd immunity, adherence to health protocols is still recommended due to the potential role of asymptomatic cases in transmitting the disease to other members of the community;and the presence of new variants of the virus and reduced antibody levels should be considered.

Incidence rate and predictors of COVID-19 in the two largest cities of Burkina Faso - prospective cohort study in 2021 (ANRS-COV13).

BACKGROUND: Early data on COVID-19 (based primarily on PCR testing) indicated a low burden in Sub-Saharan Africa. To better understand this, this study aimed to estimate the incidence rate and identify predictors of SARS-CoV-2 seroconversion in the two largest cities of Burkina Faso. This study is part of the EmulCOVID-19 project (ANRS-COV13). METHODS: Our study utilized the WHO Unity protocol for cohort sero-epidemiological studies of COVID-19 in general population. We conducted random sampling stratified by age group and sex. Individuals aged 10 years and older in the cities of Ouagadougou and Bobo-Dioulasso, Burkina Faso were included and surveyed at 4 time points, each 21 days apart, from March 3 to May 15, 2021. WANTAI SARS-CoV-2 Ab ELISA serological tests were used to detect total antibodies (IgM, IgG) in serum. Predictors were investigated using Cox proportional hazards regression. RESULTS: We analyzed the data from 1399 participants (1051 in Ouagadougou, 348 in Bobo-Dioulasso) who were SARS-CoV-2 seronegative at baseline and had at least one follow-up visit. The incidence rate of SARS-CoV-2 seroconversion was 14.3 cases [95%CI 13.3-15.4] per 100 person-weeks. The incidence rate was almost three times higher in Ouagadougou than in Bobo-Dioulasso (Incidence rate ratio: IRR = 2.7 [2.2-3.2], p < 0.001). The highest incidence rate was reported among women aged 19-59 years in Ouagadougou (22.8 cases [19.6-26.4] per 100 person-weeks) and the lowest among participants aged 60 years and over in Bobo-Dioulasso, 6.3 cases [4.6-8.6] per 100 person-weeks. Multivariable analysis showed that participants aged 19 years and older were almost twice as likely to seroconvert during the study period compared with those aged 10 to 18 years (Hazard ratio: HR = 1.7 [1.3-2.3], p < 0.001). Those aged 10-18 years exhibited more asymptomatic forms than those aged 19 years and older, among those who achieved seroconversion (72.9% vs. 40.4%, p < 0.001). CONCLUSION: The spread of COVID-19 is more rapid in adults and in large cities. Strategies to control this pandemic in Burkina Faso, must take this into account. Adults living in large cities should be the priority targets for vaccination efforts against COVID-19.

Seroprevalence of SARS-CoV-2: Insights into the epidemiology of the pandemic.

AIM: This study aimed to assess the seroprevalence of SARS-CoV-2 and disease symptoms in Malakand, Pakistan. MATERIALS & METHOD: 623 samples with suspected SARS-CoV-2 were collected from different regions of Malakand and analyzed to detect SARS-CoV-2 IgG antibodies using ELISA. RESULTS: 306 (49.1%) 0 f 623 patients were anti-SARS-CoV-2 IgG reactive, with a higher prevalence in males (75%) than females (25%). In this study, we enrolled two groups, subjects working in a non-medical setting and subjects working in a medical setting. Clinical symptoms were statistically linked with SARS-CoV-2. Four weeks of follow-up analysis of IgG titers in health care workers showed an increase in IgG antibodies titer. CONCLUSION: This study gives insights into the community-based spread of SARS-CoV-2 infection, associated immunity, and herd immunity in the studied population. This study can provide insights to the government about early vaccination of this population as most of the population is not yet vaccinated.

Incidence and sero-surveillance of feline viruses in Korean cats residing in Gyeonggi-do

Incidences of major feline viral diseases provide basic information for preventing viral disease in cats. Despite the growing interest in feline viral diseases, sero-surveillances have been lacking. In this study, we analyzed the diagnoses of feline viral diseases and conducted a sero surveillance of feline panleukopenia virus (FPV), feline calicivirus (FCV), feline herpesvirus-1 (FHV-1), and feline infectious peritonitis virus (FIPV) in Korean cats. Of the 204 confirmed cases since 2015, the numbers of diagnoses for FPV, FIPV, FCV, feline influenza virus, and FHV-1 were 156, 32, 12, 3, and 1 case, respectively. In total, 200 sera, collected between 2019 and 2021, were screened for the presence of antibodies against FPV, 2 FCVs, FHV-1, and FIPV using a hemagglutination inhibition test and a virus-neutralizing assay (VNA). The overall seropositive rates in cats tested for FPV, the 2 FCVs, FHV-1, and FIPV were 92.5%. 42.0%, 37.0%, 52.0%, and 14.0%, respectively. A low correlation (r = 0.466) was detected between the VNA titers of 2 FCV strains. The highest incidence and seropositive rate of FPV reveal that FPV is circulating in Korean cats. The low r-value between 2 FCVs suggests that a new feline vaccine containing the 2 kinds of FCVs is required.

The SARS-CoV-2 Infection Among Students in the University of Porto: A Cross-Sectional Study.

Objective: We aimed to quantify SARS-CoV-2 specific antibodies' seroprevalence among university students in Porto. Methods: A rapid point of care testing for SARS-CoV-2 specific immunoglobulin (Ig) M and IgG antibodies was performed, and a questionnaire was applied to 6512 voluntary students from September to December 2020. We computed the apparent IgM, IgG, and IgM or IgG prevalence, and the true prevalence and 95% credible intervals (95% CI) using Bayesian inference. Results: We found an apparent prevalence (IgM or IgG) of 9.7%, the true prevalence being 7.9% (95% CI 4.9-11.1). Prevalence was significantly higher among males (10.9% vs. 9.2%), international students (18.1% vs. 10.4% local vs. 8.8% nationally displaced), and increased with age. Those with a known risk contact, that experienced quarantine, had symptoms, or a previous negative molecular test had a higher seroprevalence. Of the 91 (1.4%) students who reported a molecular diagnosis, 86.8% were reactive for IgM or IgG. Conclusion: Based on immunological evidence infection was 5.6-fold the reported molecular diagnosis. The higher seroprevalence among male, older, and international students emphasizes the importance of identifying particular groups.

Ssessment of post-vaccination collective immunity against new coronavirus infection (COVID-19) among servicemen of the armed forces of the Russian Federation

The recent vaccination campaign targeting the new coronavirus infection (COVID-19) carried out in the Armed Forces of the Russian Federation, on the background of the current unstable global pandemic situation, makes it necessary to study post-vaccination population immunity to the SARS-CoV-2 virus and thus identify key features of immunity in organized military collectives. In the future, this will make it possible to objectively assess the risks of a worsening pandemic situation, effectively adjust the ongoing sanitary and anti-epidemic measures aimed at preserving and strengthening the health of military personnel, as one of the main conditions for maintaining the combat readiness of the Armed Forces of the Russian Federation. During a study conducted on epidemic indications, it was found that vaccination with Gam-Covid-Vac contributes to the formation of collective immunity with 95% effectiveness. A gender-based analysis of the immune response showed that the proportion of persons who lack class G immunoglobulins to SARS-CoV-2 among females is twice than that among men (9.3% and 4.7%, respectively). Seroprevalence indicators, classified by blood group, range from 94.4% (AB (IV) Rh-) to 97.4% (A (II) Rh-). There were no significant differences in seroprevalence between groups of people with different blood groups;however, the highest value of seroprevalence was seen among military personnel with blood group A (II) Rh-. In this context, it is advisable to continue monitoring the formation of immunity in individuals with various blood groups. The results obtained made it possible to form a primary medical and social "portrait" of a serviceman with the most adequate immune response to the introduction of the Gam-Covid-Vac vaccine (a man under the age of 20 with blood type A (II) Rh-) and to draw a conclusion about the high effectiveness of vaccination in military units (formations) staffed by conscripts and military educational organizations.

New Technological Developments in Identification and Monitoring of New and Emerging Infections

Human population growth, globalization, and climate change may pose a sustained risk of emerging infections of pandemic potential. Fortunately, technological development provides tools to identify and monitor emerging epidemics. The rapid full genome characterization of the SARS coronavirus-2 (SARS-CoV-2), responsible for coronavirus infectious disease 2019 (COVID-19), and free sharing of sequence information, enabled a rapid global response. This included diagnostics, epidemiological monitoring, nonmedical interventions, and vaccine development, limiting the pandemic impact. An early and efficient response to global health threats will continue to rely on the development, refinement, and utilization of novel technologies to detect and monitor emerging infectious diseases. © 2022 Elsevier Inc. All rights reserved.

Investigation of seroprevalence of SARS-CoV-2 IgG antibodies among healthcare workers in a tertiary care centre in district Amritsar

Background: SARS-CoV-2 infection poses tremendous challenge to the healthcare system of nations across the globe. Healthcare workers (HCWs) are crucial to the ongoing response to the SARS-CoV-2 pandemic. During the course of their work, they are exposed to hazards that place them at the risk of infection. Serological testing for SARS-CoV2 among healthcare workers, which form a high risk group helps in identifying the burden of hidden infection in an institutional setting. The present study aims to investigate the seroprevalence of IgG antibodies against SARS-CoV-2 among HCWs during 1st and 2nd wave. Material & Methods: A prospective study was conducted at Viral Research and Diagnostic Laboratory, Government Medical College, Amritsar during June July 2020 (1st wave)and April May 2021(2nd wave). During this period, 184 blood samples were collected from healthcare workers from Government Medical College and Hospital, Amritsar. Serum was separated and used for detection of Anti-SARS-CoV-2 IgG antibodies by ELISA technique. Results: Out of the 184 samples, 79 (42.9%) were found to be seropositive. Higher seropositivity was seen i.e 60.8% during the 2nd wave (April-May 2021) as compared to 25% during 1st wave. The increase in seroprevalence was observed in almost all categories of HCWs, Doctors 44.4% vz 13.04%, nurses 54.8% vz 34.7%, lab technicians 72% vz 30.4% and housekeeping staff 72.2% vz 21.7%. Also the unvaccinated HCWs showed higher seroprevalence during the second wave and 87.5% of vaccinated HCWs had demonstrable IgG antibodies. Conclusions: High seropositivity was observed among healthcare workers due to their nature of work. Rise of seropositivity among unvaccinated HCWs during 2nd wave concludes that increase in seroprevalence was attributable to natural infection. The vaccine's immunological response was also highlighted in the study.

SARS-CoV-2 Serology Across Scales: A Framework for Unbiased Estimation of Cumulative Incidence Incorporating Antibody Kinetics and Epidemic Recency.

Serosurveys are a key resource for measuring SARS-CoV-2 population exposure. A growing body of evidence suggests that asymptomatic and mild infections (together making up over 95% of all infections) are associated with lower antibody titers than severe infections. Antibody levels also peak a few weeks after infection and decay gradually. We developed a statistical approach to produce estimates of cumulative incidence from raw seroprevalence survey results that account for these sources of spectrum bias. We incorporate data on antibody responses on multiple assays from a post-infection longitudinal cohort, along with epidemic time series to account for the timing of a serosurvey relative to how recently individuals may have been infected. We applied this method to produce estimates of cumulative incidence from five large-scale SARS-CoV-2 serosurveys across different settings and study designs. We identify substantial differences between raw seroprevalence and cumulative incidence of over two-fold in the results of some surveys, and provide a tool for practitioners to generate cumulative incidence estimates with pre-set or custom parameter values. While unprecedented efforts have been launched to generate SARS-CoV-2 seroprevalence estimates over this past year, interpretation of results from these studies requires properly accounting for both population-level epidemiologic context and individual-level immune dynamics.

Seroepidemiology and risk factors for SARS-CoV-2 infection among household members of food processing and farm workers in North Carolina.

Background: Racial and ethnic minorities have borne a disproportionate burden from coronavirus disease 2019 (COVID-19). Certain essential occupations, including food processing and farm work, employ large numbers of Hispanic migrant workers and have been shown to carry an especially high risk of infection. Methods: This observational cohort study measured the seroprevalence of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and assessed the risk factors for seropositivity among food processing and farm workers, and members of their households, in North Carolina, USA. Participants completed questionnaires, blood samples were collected, and an enzyme-linked immunosorbent assay was used to assess SARS-CoV-2 seropositivity. Univariate and multi-variate analyses were undertaken to identify risk factors associated with seropositivity, using generalized estimating equations to account for household clustering. Findings: Among the 218 participants, 94.5% were Hispanic, and SARS-CoV-2 seropositivity was 50.0%. Most seropositive individuals did not report a history of illness compatible with COVID-19. Attending church, having a prior history of COVID-19, having a seropositive household member, and speaking Spanish as one's primary language were associated with SARS-CoV-2 seropositivity, while preventive behaviours were not. Interpretation: These findings underscore the substantial burden of COVID-19 among a population of mostly Hispanic essential workers and their households in rural North Carolina. This study contributes to a large body of evidence showing that Hispanic Americans have suffered a disproportionate burden of COVID-19. This study also highlights the epidemiologic importance of viral transmission within the household.

Seroprevalence of SARS-CoV-2 in hospital workers in the southern region of Minas Gerais state in Brazil: An analysis of the pre-vaccine period.

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection seroprevalence can be performed by detecting anti-SARS-CoV-2 antibodies. The survey is essential to understand the disease transmission's dynamic in the studied population. This study aimed to carry out a seroepidemiological survey of SARS-CoV-2 in three hospitals located in the south of Minas Gerais state, Brazil. 859 samples were collected from August to December 2020 when SARS-CoV-2 vaccines were still not available and Enzyme-linked immunosorbent assays (ELISA) were performed on participants sera. The average age of participants was 38 years, and most were women (71.4%). Likewise, most participants were classified as health professionals with direct or indirect contact with patients with COVID-19 (74.5%). The other participants tested belonged to other sectors, such as the administrative one (11,6%). Considering clinical symptoms, 15.8% of participants reported diarrhoea, 6.4% fever, 5.8% respiratory distress, and 7.0% loss of smell and taste. Many participants reported contact with infected patients (63.35%). Regarding the ELISA tests, 21.6% of the participants had positive results and hospital 3 had the highest positivity (21.7%), followed by hospital 2 (21.6%) and hospital 1 (20.3%). The prevalence was higher in women compared to men (22,8% and 18,7%, respectively). Regarding the area of expertise, the highest positivity (20.9%) was observed among health professionals. However, professionals who worked exclusively with COVID-19 had lower positivity when compared to professionals who did not work directly with COVID-19 (22.0% and 21.5%, respectively). When analysing the correlation between the ELISA tests with the other variables, a significant association was detected with these previous serological variables, previous contact with COVID-19 and the presence of fever symptoms, loss of smell and taste. Clinical symptoms associated with serological tests are important tools for monitoring the disease among health professionals.

Transmission of SARS-CoV-2 associated with wastewater treatment: a seroprevalence study

The detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during wastewater treatment leads to concerns about whether this process may represent a focal point for the transmission of COVID-19. An epidemiological analysis, based on a COVID-19 IgG/IgM Rapid Test Cassette, performed on 134 wastewater workers from 59 wastewater treatment plants from the province of Granada (Spain) showed a seroprevalence of 8.95% in IgG for SARS-CoV-2, which is similar to the incidence rate found for the general population of the province (9.6%;95%CI = 7.2-12.8). These findings suggest that current safety measures are sufficient for the protection of workers against SARS-CoV-2.

Seroepidemiologic Investigation of a COVID-19 Outbreak Aboard a U.S. Navy Ship

The crew of USS Kidd experienced a COVID-19 outbreak identified in April 2020. This is the earliest documented COVID-19 study with RT-PCR, serology, and pre-exposure test data on the entirety of the exposed population (n=333). Case definitions included 121 confirmed (36.3% of crewmembers) and 18 probable (5.4% of crewmembers) based on laboratory diagnostic test results. At the time of testing positive, 62 (44.6%) cases reported no symptoms. Hispanic ethnicity (AOR: 2.71, CI: 1.40-5.25) and non-smoker status (AOR: 2.28, CI: 1.26-4.12) were identified as statistically significant risk factors. This study highlights the value of rapid, onboard diagnostic testing to quickly identify an outbreak and enumerate cases, as well as the serological testing to flag potential cases missed with standard viral case identification methodologies.

Performance of the PanbioTM COVID-19 Ag rapid test in a health care setting in Ouagadougou, Burkina Faso

This study aimed to evaluate the performance of the PanbioTM Covid-19 Ag Rapid Test (Abbott) in a medical center in Ouagadougou. The PanbioTM COVID-19 Ag test was evaluated from January 26 to March 31, 2021 in symptomatic and asymptomatic patients in the medical Centre of Kossodo. A total of 268 individuals were tested by both SARS-CoV-2 RT-PCR, and antigen RDT. Of these 268 individuals, 52 were positive and 216 were negative for COVID-19 RT-PCR. The performance parameters of the test and its Kappa agreement with the RT-PCR were calculated according to the presence or absence of symptoms in the patients on one hand, and according to the time onset of symptoms on the other hand. The sensitivity of the PanbioTM COVID-19 Ag Rapid Test ranged from 29.63% (95% CI: 13.75 to 50.18) among COVID-19 asymptomatic patients, to 87.5% (95% CI: 52.91 to97.76) among symptomatic patients with symptom onset time of 1-5 days. Similarly, the PanbioTM COVID-19 Ag Rapid Test specificity was 97.3% (95% CI: 90.58 to 99.67) and 96.4% (95% CI: 91.81 to 98.82) in symptomatic and asymptomatic RT PCR negative patients. The PanbioTM COVID-19 Ag Rapid Test shows good performance in detecting COVID-19 cases in patients with a symptom onset time of less than seven (7) days. This performance is even better when the symptom onset is reduced to five (5) days. The results show that the antigen RDT is not suitable for COVID-19 detection among asymptomatic patients.

Duration of MERS - Coronavirus antibodies in a small closed dromedary camel herd in Dubai

This investigation shows that MERS-CoV ELISA antibodies remain in dromedary camels at least for 9 years, most probably lifelong. The viral infection was most likely acquired at a young age when maternal antibodies have receded between 4 to 8 month of age. Additionally, in the investigated herd, the 4 ELISA antibody negative dromedary camels remained negative also for 9 years, indicating, that no MERS-CoV was circulating in the herd. Until today, the specific source of MERS-CoV infection for young dromedaries remains unknown.

Studying the efficacy, safety, and immunogenicity of the covishield vaccine in healthcare personnel in an Indian scenario

Background: COVID-19 has largely affected humans with high infection spread and mortality rates globally including India with no specific vaccine or therapy proven effective for its management as the immune response to COVID-19 is not well understood. Covishield has been largely distributed and administered in Indian subjects. However, its efficacy and safety are still unclear raising doubts. Aim: The present study aimed to assess the efficacy, safety, and immunogenicity of the Covishield vaccine in healthcare personnel in India. Methods: In 244 healthcare workers, SARS CoV2 IgG antibodies were assessed before and following the vaccination with two doses of Covishield given at 4 to 6 weeks apart. The efficacy of the vaccine and adverse effects after immunization were evaluated till two months after vaccination. The most common side-effect seen after the 1st dose was pain at the site of injection reported in 53.27% (n=130) study subjects followed by fever in 27.86% (n=68) study subjects, body ache in 22.95% (n=56) study subjects Results: Before vaccination, IgG was positive in 21.31% (n=52) study subjects and was negative in 78.68% (n=192) study subjects. Post-vaccination, IgG-positive status was seen in 69.67% (n=170) study subjects and was not seen in 30.32% (n=74) study subjects. In the infected group having 62 subjects, post-vaccination IgG positive was seen in 96.77% (n=60) study subjects and not seen in 3.22% (n=2) study subjects. In the uninfected group including the 182 subjects, post vaccination IgG positive was seen in 60.43% (n=110) study subjects and was not seen in 39.56% (n=72) study subjects respectively. After 2nd dose, the most common side-effect was pain at the site of injection seen in 24.59% (n=60) study subjects followed by headache in 12.29% (n=30) study subjects, fever in 7.37% (n=18) study subjects, body ache in 3.27% (n=8) participants, low backache and fatigue in 1.63% (n=4) study subjects each and local swelling in 0.81% (n=2) study subjects respectively. All the side effects had a non-significant difference except body ache which was significantly higher after 1st dose with p=0.02. Conclusion: Covishield vaccine has acceptable safety profile levels with increased seropositivity with more intervals in the two doses of the Covishield vaccine. Covishield does not prevent breakthrough infection. However, it can reduce the infection severity of COVID-19.

The Seroprevalence and Seropositivity of SARS-CoV-2 among Healthcare Workers during the Third Pandemic Wave.

BACKGROUND: Due to the unclear protective role of produced antibodies and the need for seroepidemiologic studies, we surveyed the COVID-19 seroprevalence among healthcare professionals who had direct or indirect contact with COVID-19 patients. METHODS: From 19 October 2020 to 17 February 2021, 300 healthcare workers were enrolled and tested for serum antibodies in this prospective cohort study. Demographic information, risk factors, and infection history were collected. Anti- SARS-CoV-2 IgG and IgM antibody titers were determined to estimate the seroconversion rate. RESULTS: During the first and second phases of the study, the positive seroconversion rates were 31.7 and 26.6%, respectively. In seronegative individuals, sixteen (10.6%) new cases of COVID-19 and five (6.3%) reinfections were identified. Among those with a positive antibody level, forty-one (36.9%) healthcare workers reported no symptoms in the preceding months. There was no association between occupational exposure and an increased probability of seroconversion. CONCLUSIONS: The seropositivity rate and the rate of asymptomatic individuals with seroconversion was remarkable and could be an indicator of a high infection rate among healthcare workers.