The seed stock is the cultured virus, which has the highest vaccine immunity and is commonly present in majority of the affected cases. If the vaccine is developed from the seed virus then it is likely to be effective for other strains.

In India, three pharmaceutical companies - Serum Institute of India, Bharat Biotech and Panacea Biotech - are working on developing the vaccine.

The WHO is already collaborating with the Serum Institute of India for developing a seasonal flu vaccine.

Dayal said Serum Institute of India has made a lot of progress and started animal testing of the vaccine.