Serums or antitoxins are used. These are obtained from the blood of humans or animals that have already developed the antibodies for fighting the disease. Usually the blood is processed and the blood fraction (gamma globulin) containing the antibodies is separated and made into a serum.

What, then, of the use of a serum containing only a minute fraction of blood and employed to supply an auxiliary defense against some infection and not employed to perform the life-sustaining function that blood normally carries out?

We believe that here the conscience of each Christian must decide. Some may feel that accepting such a serum does not constitute an act of disrespect for the sacredness of life and of God as the life Source, that it does not constitute a flouting of God’s expressed will concerning the use of blood to feed the body. On the other hand, the conscience of others may call on them to reject all such serums. Each must answer to God as his or her judge with regard to the reason for one’s conscientious decision.​—1 Cor. 4:4; 2 Cor. 5:10.b

While refraining from approving or condemning in such areas where we believe the decision must be left to individual conscience, we do, nevertheless, urge all to seek to maintain their conscience clean before God, never showing deliberate disrespect for his Word.​—1 Pet. 3:16; 1 Tim. 1:19.

Also, in cases where there is an Rh incompatibility between a mother and her newborn child, doctors may urge her to accept a specialized serum injection. If the mother has not yet become sensitized to the child’s blood type, the serum (made from the blood of a woman who has already produced the antibodies) might be administered so her system does not produce antibodies that might adversely affect a future child.