Comparative study of clinical features and vaccination status in Omicron and non-Omicron infected patients during the third wave in Mumbai, India

Abstract

Objectives: The Omicron variant–mediated COVID-19 wave is responsible for a global tsunami of cases. There is scarce data about the clinical and epidemiological characteristic analyses of the third wave. We present the data of COVID-19 patients from Mumbai region during the early third wave by taking S-gene target failure (SGTF) as a proxy for probable Omicron cases. Methods: We collected retrospective data of RT-PCR-confirmed (COVID-19) patients, and measured the proportion of possible Omicron cases by SGTF. We segregated and analyzed the clinical and lab data of patients with outcomes such as differing symptoms, vaccination coverage, previous infection, and travel history. We also performed a trend analysis of Mumbai’s COVID-19 data before and during the third wave. Results: All patients had mild clinical symptoms while few were asymptomatic. Myalgia was more significantly present in SGTF/Omicron cases compared to non-SGTF/Delta patients. Out of the total 101 COVID-positive individuals, 94 individuals (93%) had taken two doses of COVID vaccine. Among these 94 individuals, 9 (8.9%) had been previously infected with COVID 19 in the first or second waves. 77.7% of the previously infected were now infected with Omicron variant and only 22.3% by a non-Omicron variant. Conclusion: Rapid rise and fall during the third wave in Mumbai was due to Omicron cases gradually replacing Delta. The overall milder clinical spectrum in both Omicron and Delta cases imply that vaccines might not be effective against re-infection but can attenuate disease severity and mortality, as evident by high coverage of vaccination in the country.

COVID-19 vaccination: disease status and outcomes of COVID-19 patients admitted in tertiary care hospital in Raigad District of Maharashtra

“…Till December 2021 the number of COVID-19 cases were below 10,000 from then, India witnessed its third wave with sudden rise in incidence of COVID-19 infection with omicron variant. 7 During this period nearly 90% of Indian adult population has received at least one dose of COVID-19 vaccine but still most vaccinated individuals got re-infected with the virus. This showed that the role of vaccine in reducing the transmission of the disease was limited.…”

“…Takke et al found mild clinical symptoms in vaccinated COVID positive patients. Vaccines might not be effective against re-infection but can attenuate disease severity and mortality, as evident by high coverage of vaccination in the country 7. Unvaccinated elderly patients were more affected and had poor outcomes than younger population to support this finding, a study conducted by Sara et al concluded that Coronavirus disease 2019 (COVID-19) caused by the virus is particularly severe in older individuals because they are more likely to have an impaired immune response.…”