This is the first study in India which provides the evidence of Omicron community transmission with significantly increased breakthrough infections, decreased hospitalisation and symptomatic infection rate among individuals with high seropositivity against SARS CoV-2 infections.

 

The study conducted by the Institute of Liver and Biliary Sciences, is based on epidemiological, clinical and genome sequence analysis of 264 cases since the day Omicron was designated as VoC by WHO.

 

Out of the 264 cases included during study period, 68.9 per cent were identified as Delta and its sub-lineages while 31.06 per cent were Omicron with BA.1 as the predominant sub-lineage (73.1 per cent).

 

Most of the Omicron cases were asymptomatic (nP,61 per cent) and not requiring any hospitalisations. A total of 72 (87.8 per cent) cases were fully vaccinated.

 

At least 39.1 per cent had a history of travel or contact while 60.9 per cent showed community transmission. A steep increase in the daily progression of Omicron cases with its preponderance in the community was observed from 1.8 per cent to 54 per cent, the study highlighted.

 

The study observed that young adults and males were infected more in comparison to children and elderly population which could be due to more socialising and close connections than other mentioned groups.

 

The results suggest a large reduction in protection against Omicron variant of the Covid-19 infection as 87.8 per cent population got reinfected after full primary vaccination thus implying increased breakthrough infections. The results suggest a large decrease in protection from vaccine or natural immunity against Covid infections caused by the Omicron variant.

 

This is a prospective study where respiratory specimen from all RT-PCR confirmed positive cases between November 25 to December 23 collected from five districts of Delhi were subjected to whole genome sequencing. Complete demographic and clinical details were recorded.

 

This emphasises the urgent need for booster vaccination and will warrant implementing non-pharmaceutical interventions along with the installation of rapid detection strategies for asymptomatic carriage in high-risk transmission populations especially with those having comorbidities.

 

The study has said that majority of Omicron patients (60.9 per cent) had no documented international travel history or contact hence evidently they acquired the infection locally, thus signifying the community spread and imposing further challenges in controling the virus.