Is there any other way to protect ourself from infectious diseases without vaccination or if vaccine for that particular disease is not developed yet? Yes, in fact, there is. They are called serums. Serums provide protection too. Luckily, they don't take 18 months to develop like vaccines, and no, we're not talking about the moisturising product you apply after cleansing for your skincare. In this Now You Know let's learn what they are and how they are useful.

Serums also help our body generate antibodies to fight diseases, just like vaccines but developing them is a different process. Antibodies are proteins that provide passive immunity to the body by acting against antigens.

"Serum" is the Latin word for "whey" --- the watery liquid that separates from the curds while making cheese. The factors that help our blod clot are called fibrinogens. Serum is blood plasma from which fibrinogens have been removed. For making serums, a blood sample is allowed to clot and then centrifuged to remove the clot and blood cells. Hence, it's also called blood serum. It is a clear, yellowish fluid composed of antibodies.

The watery fluid from inflamed animal tissues, like in edema or a blister can be used as serum; even the watery portion of their milk. Blood serum from the tissues of immunized animals, containing antibodies is called antiserum which can be used to transfer immunity to another individual.

All proteins not used in blood clotting is present in serum like antibodies, antigens, hormones, electrolytes, drugs or microorganisms. Serum does not contain white blood cells, red blood cells or platelets.

The serum of already recovered patients or those successfully recovering from an infectious disease can be used to treat others with that disease. Serum is used for DNA analysis too. Serum from cow foetuses is used for growth in cell culture. Serum is used in various diagnostic tests and to determine our blood types too.