Impact:

Although two vaccines against bacterial pneumonia became available in the 1940s, they were withdrawn from the market because most physicians preferred treating the disease with penicillin. Physicians at that time mistakenly believed that the antibiotic would all but eliminate the threat of pneumonia, and the manufacturer withdrew the vaccine.
Schiffman demonstrated severe limitations in treating pneumococcal infections with antibiotic therapy, and, with Robert Austrian, introduced a new vaccine in 1978. Large-scale testing during the following decade confirmed its efficacy.  However, it was not until the 1990s, with the increasing pneumococcal resistance to multiple antibiotics, that pneumococcal vaccination was widely accepted. It has since become the established standard of care for the elderly, for persons with diabetes and kidney-disease, patients with weakened immune systems, and those who have received a transplanted organ or undergone a splenectomy.

Schiffman also developed a test to measure a wide range of immune system functions and disorders.  First employed with geriatric and sickle-cell patients, the test was later used to evaluate immune system response to treatment in patients with HIV/AIDS and other disorders. His was the only laboratory to use this assay, and each year, about 100,000 samples from around the world were sent to him for analysis.