Facts have been "twisted and misrepresented" in some social media posts which suggested that indigenously developed Covaxin contains newborn calf serum, the Union Health Ministry said in a statement on Wednesday.

Newborn calf serum is used only for the preparation and growth of vero cells. Serum from bovine and other animals are standard enrichment ingredients used globally for vero cell growth, it said.

Vero cells are used to establish cell lives which help in the production of vaccines. This technique has been used for decades in developing vaccines against polio, rabies, and influenza.

After growth, the vero cells are washed in water and with chemicals, also technically known as buffer, multiple times to make them free from newborn calf serum. The vero cells are then infected with coronavirus for viral growth, the health ministry said.

The vero cells are completely destroyed in the process of viral growth. Thereafter, the grown virus is also killed (inactivated) and purified, it said.

The killed or inactivated virus is then used to make the final vaccine. No calf serum is used in the formulation of the final vaccine, according to the statement.

"Hence, the final vaccine (Covaxin) does not contain newborn calf serum at all and the calf serum is not an ingredient of the final vaccine product."