RESPIRATORY VIRUS VACCINES .5. FIELD EVALUATION FOR EFFICACY OF HEPTAVALENT VACCINE

Abstract

A mixed heptavalent respiratory virus vaccine that contained formalin-killed and concentrated respiratory syncytial virus, parainfluenza 1, 2, and 3 viruses, influenza A2 and B viruses, and Mycoplasma pneumoniae organisms was prepared in alum formulation. A controlled study to evaluate the vaccine in terms of serologic response and protective efficacy was carried out during the respiratory disease season of 1964-1965 among 407 kindergarten and nursery school children in the Havertown-Springfield community, a suburban area of Philadelphia. The vaccine given in 3 doses one month apart to 199 children stimulated homologous antibody in 94% or more of persons initially seronegatlve to the parainfluenza and influenza viruses; in 79% of those seronegative to Mycoplasma pneumoniae, and in 33% of those without antibody to respiratory syncytial virus. The vaccine afforded a 36% reduction in occurrence of severe respiratory illness and 15% reduction in total respiratory illness during the 1st 10 weeks of observation (January-February), but no effect was apparent during the subsequent 9 weeks when the over-all respiratory disease rates were low. The finding of protective efficacy was significant and was substantiated in analyses of average occurrence of respiratory illness per child and in average illness scores assigned to the cases. The rates for recovery of viruses and mycoplasma from the patients were so low as to preclude estimation of agent-specific attack rates. The marked absence of influenza A2 in the hiladelphia area during the period of study, the occurrence of influenza B only during the late period of observation, and the serologic response data together with the agent isolation results supported the judgment that the vaccine efficacy was due mainly to the parainfluenza and mycoplasma components. The findings in the present study were viewed as highly promising and as indicative that substantial protection against acute respiratory illnesses can be achieved by prophylactic immunization.