Community transmission of Omicron variant? Over 60 per cent of infected people in Delhi without travel history
New Delhi, Jan 16: More than 60 per cent of the people infected with the Omicron variant of the coronavirus in the national capital did not have any travel history or contact with international travellers, suggesting that its community transmission had happened quite fast, according to a study by the Delhi government-run Institute of Liver and Biliary Sciences.
The study, possibly the first in India to provide evidence of community transmission of Omicron, looked into genome sequencing data of positive cases collected from five districts of Delhi -- South, Southeast, Southwest, West and East -- between November 25 and December 23 last year.
A total of 332 samples were sent to ILBS from different testing laboratories across the five districts and out of these, 264 samples that passed "quality check" were analysed. Out of the 264 samples sequenced, 68.9 per cent were found infected with Delta and its sub-lineages while the remaining 82 samples (31.06 per cent) were Omicron. In Delhi, the first two cases of Omicron were detected in the first week of December.
The study conducted by the Department of Clinical Virology of the facility observed a steep increase in the daily progression of Omicron cases with its preponderance in the community from 1.8 per cent to 54 per cent. Among the 82 cases, 46.3 per cent belonged to a total of 14 families and out of these, only four families had documented trave history.
Out of the remaining 10 families with no travel history, three families contracted the infection after coming in contact with a non-family member with travel history.
"Rest of the 20 individuals from seven families contracted the infection possibly due to community transmission," it said.
The study stated that 39.1 per cent of the people with Omicron had a history of travel and/or contacts, while 60.9 per cent showed community transmission. "Our findings strongly suggest that Omicron has a much higher rate of asymptomatic carriage resulting in high prevalence of asymptomatic infection, a likely major factor in the rapid dissemination of the variant locally and globally. Our results suggest a large decrease in protection from vaccine or natural immunity against COVID-19 infections caused by the Omicron variant," noted the study.
Out of 82 Omicron patients, 72 were fully vaccinated with 56 per cent of the individuals having received Covishield, followed by Covaxin (12 per cent), Pfizer (11 per cent), Moderna (four per cent), Sputnik V (four per cent) and Johnson and Johnson (one per cent). The study also stressed on the urgent need for booster vaccination.
According to an official, it was after the findings of this study that Health Minister Satyendar Jain had announced the community transmission of Omicron. On December 30, Jain had said that Omicron was gradually spreading in the community and the new, fast-spreading variant of concern had been found in 54 per cent of the latest samples analysed in the national capital.