NEW DELHI - Chief scientist at the World Health Organisation (WHO) Soumya Swaminathan Thursday warned against the idea of attaining herd immunity through natural infection to fight the COVID-19 pandemic, calling it "foolish" as there are huge costs to be paid.

"Herd immunity through natural infection is a very foolish idea we have said from the beginning because there is a huge human cost to be paid," said Swaminathan in an interview with New Delhi-based television news channel NDTV 24/7.

She said that India has followed a good policy of vaccination, adding that "my understanding is that over 90 percent of adults now have received at least one dose and over three-fourths have received the full vaccination coverage."

The WHO chief scientist said the new Omicron sub-variant BA.2 is more potent than BA.1 and its transmission is more than other sub-variants.

Swaminathan said the WHO can not yet comment on the impact of Omicron as it was a relatively new variant and studies were still ongoing to determine if it can cause reinfection and how it affects long-term immunity.

"Two months is too little time to know if it causes reinfection and how it affects long-term immunity. We saw some studies where the blood of patients who recovered from the new variant helped with Delta infection but we don't know if that will be true for future variants," she said.

She said the vaccines that are being used for protection in terms of reducing hospitalisations and deaths were working very well.

"All of them help us. The elderly and vulnerable are much better protected now. It shows that the vaccines are effective and a good defence mechanism," she said.

At present India is in the grip of the third wave of COVID-19. However, the daily caseload of COVID-19 has begun to fall.

The federal Health Ministry reported on Thursday morning 172,433 new cases and 1,008 more deaths of COVID-19, bringing the total infections to 41,803,318 and taking the death toll to 498,983 in India.