The overall threat posed by Omicron largely depends on three key questions - its transmissibility; how well the vaccines and prior SARS-CoV-2 infection protect against it, and how virulent the variant is as compared to other variants.
Currently, Covishield and other COVID-19 vaccines are approved for people above the age of 18.
TN minister Ma Subramanian said their samples tested positive for COVID-19 along with S-gene dropout, a marker for Omicron.
So far, Maharashtra has reported the highest number of cases at 28, followed by Rajasthan at 17. Omicron cases have also been reported in Karnataka, Gujarat, Kerala, AP, Delhi and Chandigarh.
The presence of Omicron has already been confirmed in almost 40 countries, including India.
Omicron cases have now been reported in India, Japan, Malaysia, Singapore and South Korea, and new cases are being documented with each passing hour.
No Omicron-linked deaths have yet been reported though the WHO has said it poses a high risk of infection surges.
WHO urged its 194 member states to accelerate vaccination of high-priority groups and ensure plans were in place to maintain health services.
Travellers from other countries will be allowed to leave the airport and shall self-monitor their health for 14 days.
The WHO said Omicron, initially detected in South Africa, may spread more quickly than other forms.