HOMOLOGOUS AND HETEROLOGOUS ANTIBODY RESPONSE OF INFANTS AND CHILDREN TO MULTIPLE INJECTIONS OF A SINGLE STRAIN OF INFLUENZA VIRUS 12

Abstract

Multiple subcut. injns. in children, whose avg. age was 3.2 yrs., of an influenza virus vaccine containing the type A PR8 strain, gave greater rises in mean titer of erythrocyte agglutination-inhibiting antibody against the homologous strain than did a single injn. of the same virus prepn. In children of 4 yrs. of age or older, who were living at the time of the last previous epidemic of influenza A in the area, the max. response was obtained after a single large dose. Rises in titer to three other type A strains tested also occurred. Rises in titer to 2 strains of swine influenza virus were less pronounced. The height of antibody response to the heterologous strains was apparently influenced by the intimacy of their antigenic relationship to the PR8 strain and was not progressively enhanced as the admn. of vaccine was continued beyond 3 doses. The significance of the antigenic variation of strains, dosage, and schedule of injns. of influenza virus vaccine in children is discussed. It was concluded that a reasonable schedule would seem to be the use of 3 injns. of the equivalent of 0.3 ml. of infected, unconcentrated allantoic fluid spaced at weekly intervals. The use of concd, material in infants and young children is not advisable unless the vaccine prepn. is diluted prior to use.