Omicron's explosive spread potential makes threat level very high globally, says Insacog

Omicron's explosive spread potential makes the threat level very high globally, especially in regions with low population immunity, INSACOG has said and noted higher population immunity due to infections and vaccination was behind the apparent reduction in severity compared to Delta and other variants.

In its weekly bulletin of December 27, released on Monday, the Indian SARS-CoV-2 Genomics Consortium (INSACOG) said global outbreaks of SARS-CoV-2 are increasingly shifting from Delta to Omicron.

''Omicron has a clear growth advantage over Delta with the highest level of immune escape so far as well as high intrinsic transmissibility, leading to larger outbreaks than seen with Delta. Estimates of the severity of illness associated with Omicron are lower than seen in previous outbreaks,'' it said citing global data.

The difference in severity between Omicron and Delta measured over the same time period is smaller, suggesting that the majority of the apparent reduction in severity, compared to previous outbreaks, is because of higher population immunity from previous infections and vaccination, the INSACOG said.

It noted that based on all available data, older non-immune subjects are still likely to be at risk for severe disease, comparable to previous variants.

In view of Omicron's explosive spread potential, the threat level is still very high, especially in regions with low population immunity, the INSACOG said.

''Adjusted estimates of the hazard ratio for hospital attendance for Omicron vs Delta cases in the UK suggest that risk for unvaccinated is only about 25 per cent lower for the same period.

''Importantly, in the UK, individuals who have received at least two doses of either AstraZeneca/Covishield or mRNA vaccines remained substantially protected against hospitalisation, even if protection against infection was largely lost against the Omicron variant,'' it said. As many as 4,033 cases of the Omicron variant have been reported so far across 27 states and Union territories.