From the above data, it is apparent that there is very little to indicate that an immunity to epidemic influenza is conferred by the use of a prophylactic vaccine composed of inert Pfeiffer bacilli alone. If a desirable vaccine is to be obtained through the use of these organisms, there must be radical changes in the mode of preparation of the vaccine or in the size of the doses given. _The Attempt to Protect Against Epidemic Influenza by the Use of Mixed Vaccines_ For some years commercial houses have been carrying mixed vaccines for the treatment of colds, which they called influenza vaccines. These preparations were made up usually of six or more different varieties of bacteria, and all of them were of similar composition. There was more or less variation in the doses, both as far as the total number of bacteria and the relative number of the different types were concerned. A typical example of a so-called “mixed influenza vaccine” may be given about as follows: B. Influenza (Pfeiffer) 25 to 400 million per c.c. M. Catarrhalis 25 to 400 million per c.c. B. Friedlander 25 to 400 million per c.c. Pneumococci 25 to 400 million per c.c. Streptococci 25 to 400 million per c.c. Staph. Albus-Aureus 50 to 800 million per c.c. ——— ———— Totals 175 to 2800 million per c.c. These vaccines were recommended in the various catalogues for use either alone or together with other vaccines in the prophylaxis and treatment of common colds, and in acute and chronic diseases of the respiratory tract. As a matter of fact, they had been used very little in prophylaxis, and had failed to show very much value in treatment. In discussing these vaccines from the standpoint of treatment, R. M. Pearce (13) had the following to say: “A mixed vaccine for common ‘colds’ containing several organisms (staphylococcus, streptococcus, pneumococcus, micrococcus catarrhalis group, bacillus of Friedlander group, diphtheroid group, bacillus influenza) is one of the most recent bacterial ‘shotgun’ mixtures, which takes the chance of one lucky bull’s-eye in seven shots.” “No one can claim a scientific or even a common-sense basis for the treatment of a cold by such a mixture.” Catarrhal mixed vaccines of a similar kind were refused acceptance by the committee on “New and Non-efficial Remedies” of the American Medical Association, in June, 1918 (14), on the grounds that insufficient evidence of their therapeutic value had been furnished by their manufacturers.