State governments have been asked to take a national approach in engaging the drug companies and deciding the criteria for coronavirus vaccine, Niti Aayog Member VK Paul said on Tuesday.

He was responding to a question on the BJP's poll promise of "free vaccine" in Bihar.

The BJP's Bihar election manifesto, released by Union Finance Minister Nirmala Sitharaman, said that every person in Bihar would be given free Covid-19 vaccine once it is ready. Since then, the Congress and BJP have been crossing swords over the issue.

At a press conference here, Paul said: "We have requested the state governments to wait for the overall picture to become clear and take a national approach in engaging the companies and deciding  the criteria for vaccine. The state governments have made these statements and they should be respected."

"Vaccine scenario is dynamic. An approach is being fine-tuned, blueprints are being done and preparations are being done to deliver vaccine to the priority groups. There is absolutely no problem in terms of resources."

Three vaccine candidates are currently in different stages of clinical testing - Covaxin has got approval for Phase-III trials, Cadila is also progressing with Phase-II trials and the Serum Institute of India is completing phase IIb trial.

ICMR chief Balram Bhargava, who was also present, dwelt on the co-relation of pollution with Covid-19 deaths. "There have been some studies from Europe and the United States where they have looked at polluted areas and compared mortality during lockdown and correlation with pollution and found clearly that pollution is contributing to mortality in Covid-19."

"They have found particles of the virus in PM 2.5 particles. Pollution is a major contributor and the most inexpensive treatment and prevention from Covid-19 is a rapid adoption of wearing a mask. Wear mask for Covid and pollution and we will get double  advantage."

The national capital has been witnessing a spike in the air pollution, with some areas recording severe air quality.