“…The actual weight of inactivated virus injected into each rabbit was, however, only about 50jtg., of which only an unknown proportion consisted of immunizing antigen. In the same year Levinson, Milzer, Shaughnessy, Neal & Oppenheimer (1945) reported a new method for the production of potent inactivated vaccines with ultra-violet irradiation. Technical details were not available at that time, but bacteria and viruses were described as inactivated 'in a fraction of a second by exposing continuously flowing thin films with a depth of less than 1 mm.…”