Clinical profile of patients infected with suspected SARS-CoV-2 Omicron variant of concern, Tamil Nadu, India, December 2021-January 2022.

Background & objectives: COVID-19 cases have been rising rapidly in countries where the SARS-CoV-2 variant of concern (VOC), Omicron (B.1.1.529) has been reported. We conducted a study to describe the epidemiological and clinical characteristics and outcomes of COVID-19 patients with 'S' gene target failure (SGTF, suspected Omicron). Furthermore, their clinical outcomes with COVID-19 patients with non-SGTF (non-Omicron) were also compared. Methods: This study was conducted in Tamil Nadu, India, between December 14, 2021 and January 7, 2022 among patients who underwent reverse transcription-PCR testing for SARS-CoV-2 in four laboratories with facilities for S gene screening. Consecutively selected COVID-19 patients with SGTF were telephonically contacted, seven and 14 days respectively after their date of positive result to collect information on the socio-demographic characteristics, previous history of COVID-19, vaccination status and clinical course of illness along with treatment details. To compare their outcomes with non-SGTF patients, one randomly suspected non-Omicron case for every two suspected Omicron cases from the line-list were selected, matching for the date of sample collection and the testing laboratory. Results: A total of 1175 SGTF COVID-19 patients were enrolled for this study. Almost 6 per cent (n=72) reported a history of previous infection. 141 (13.5%) suspected Omicron cases were non-vaccinated, while 148 (14.2%) and 703 (67.4%) had received valid one and two doses of COVID-19 vaccines, respectively. Predominant symptoms reported included fever (n=508, 43.2%), body pain (n=275, 23.4%), running nose (n=261, 22.2%) and cough (n=249, 21.2%). Five (0.4%) of the 1175 suspected Omicron cases required oxygen supplementation as compared to ten (1.6%) of the 634 suspected non-Omicron cases. No deaths were reported among omicron suspects, whereas there were four deaths among suspected non-Omicron cases. Interpretation & conclusions: Majority of the suspected Omicron cases had a mild course of illness. The overall severity of these cases was less compared to the suspected non-Omicron cases.

Factors associated with the decay of anti-SARS-CoV-2 neutralizing antibodies among recipients of an adenoviral vector-based AZD1222 and a whole-virion inactivated (BBV152) vaccine in Chennai, India: a cross-sectional cohort study (preprint)

Background: The SARS-CoV-2 has caused high rates of morbidity and mortality and is spreading globally, including in populations with high rates of vaccination. The magnitude of protection conferred after recovery from natural infection or by vaccine administration, and the duration of protective immunity developed post-vaccination, remains ambiguous. Methods: We investigated the factors associated with antibody decay in 519 individuals who received treatment for COVID-19-related illness or received COVID-19 vaccination with two commercial vaccines, viz., an adenoviral vector-based (AZD1222) and a whole-virion-based inactivated (BBV152) vaccine at the State Public Health Laboratory, and the Government Corona Hospital, Chennai, India from March 2021. Blood samples were collected during regular follow-up post-infection/vaccination and tested for their levels of anti-SARS-CoV-2 IgG. Blood collected were tested for their levels of anti-SARS-CoV-2 IgG by a commercial automated chemiluminescent immunoassay (CLIA). Findings: Age and underlying comorbidities were the two variables that were independently associated with the development of breakthrough infection. Individuals who were >60 years of age with underlying comorbid conditions had a ~15 times and ~10 times greater risk for developing a breakthrough infection and hospitalization, respectively. The time elapsed since the first booster dose was associated with attrition in anti-SARS-CoV-2 IgG, where each month passed was associated with an ebb in the neutralizing antibody levels by a coefficient of -6 units. Participants who were >60 years of age had an accelerated IgG decay rate, where each day of lapse was associated with a decrease by 23 units. Each month of lapse was associated with an increased risk of contracting a breakthrough infection and hospitalization by 0.85 and 0.85, respectively. Interpretation: Our findings advocate that the elderly with underlying comorbidities represent a high-risk group warranting more medical attention, and measures to boost anti-SARS-CoV-2 immune responses such as administering a second booster dose with both the vaccines, viz., AZD1222 and BBV152 are urgently warranted.