What is the role of animal serum in making of vaccines?

Team Udayavani, Jun 18, 2021, 1:18 PM IST

The Government on Wednesday clarified that Bharat Biotech’s Covaxin does not contain newborn calf serum at all and that the calf serum is not an ingredient of the final vaccine product.

Also, Bharat Biotech clarified that newborn calf serum is used in the manufacturing of viral vaccines.

The government said that newborn calf serum is used by all viral vaccine makers as a standard practice. It said that they are needed to grow the disease-causing virus, bacteria or other pathogens in the laboratory, but do not themselves become an ingredient of the vaccine.

Why is calf serum used? 

Bharat Biotech’s Covaxin is made of an inactivated vaccine that kills the live microorganisms of the coronavirus. This vaccine destroys the ability of the virus to multiply in the human’s body and increases immunity system to fight the virus.

Viruses need living cells with special molecules known as “growth factors” to grow properly.  A solution with 5-10 per cent of calf serum is used to provide these complex growth factors that mimic human cells.

Why only cows? 

As mentioned on the website of the Food and Drug Administration of the United States, Microorganisms for vaccine manufacture are grown under controlled conditions in media which provide the nutrients necessary for growth. Cow components are often used simply because cows are very large animals, commonly used for food, and thus much material is available.

It is also rich in some useful chemicals and enzymes. Cow milk is a source of amino acids, and sugars such as galactose. Cow tallow derivatives used in vaccine manufacture include glycerol.  Many difficult to grow microorganisms and the cells that are used to propagate viruses require the addition of serum from blood to the growth media.

Does the finished vaccine have Calf serum? 

The Centre in its statement has clarified that Newborn calf serum is used only for the preparation/growth of vero cells. The vero cells, after the growth, are washed with water, chemicals, many times to make it free from the newborn calf serum.

The vero cells are completely destroyed in the process of viral growth. Thereafter this grown virus is also killed (inactivated) and purified. This killed virus is then used to make the final vaccine, and in the final vaccine formulation, no calf serum is used. 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, the Centre added.