Summary Details are given of the method of tissue culture safety testing of inactivated poliomyelitis virus strain pools and the subsequent trivalent vaccine, as developed and utilized in the production of a formaldehyde-ultraviolet irradiation inactivated vaccine. Data obtained, using formaldehyde as the sole inactivating agent, are compared with those obtained utilizing the combination (formalin-ultraviolet) method. Certain fundamental and theoretical aspects of inactivation rate data accumulated over the past few years are discussed.
Summary An extensive series of experiments designed to establish the practicality of combining formaldehyde inactivation with ultraviolet irradiation as a method for the inactivation of poliomyelitis virus for the production of vaccines has been reviewed. The actual use of the combination method is illustrated by safety, stability and potency test data obtained in a series of experimental vaccines. These vaccines were also subjected to trial in humans. The objective has been to introduce and illustrate the feasibility of producing virus vaccines according to standards (11), particularly poliomyelitis, by the use of a combination of chemical (formaldehyde) and physical (ultraviolet) methods of inactivation.
Summary Studies of the formalin inactivation of poliomyelitis virus have shown that the reaction, under the conditions studied, does not follow first order rate laws. Inactivation rate curves plotted in accordance with the first order rate laws show that during the first few hours of the reaction there is a disproportionately great drop in infectious titer which appears on the curve as a sharp deviation from the theoretical straight line. This pattern of the reaction was apparent under varying conditions of pH, temperature, and formalin concentration. Similarly, the pattern was not affected by varying concentrations of protein and amino acids in the virus-suspending media or by subjecting virus suspensions to varying clarification procedures. Tests also indicated that the pattern of the reaction was not an artifact resulting from technical errors in sampling. The rate of the reaction varied with formalin concentration, temperature, pH, and amino acid and protein concentration of the suspending media. Practical implications of the results are presented in the discussion.
