Gamma globulin is the term of a family of blood fractions, some of which include immunoglobulins. These are present in the blood serum of the patient who has developed antibodies, and can greatly mitigate the effects of the disease. This procedure was used as a last-ditch stand against the effects of an active case of polio, in the days before a vaccine was available. It has always been scarce supply.
Any theory why those with Blood Type A may be more susceptible to the virus? And Type O less vulnerable?