Meaning of circulating antibody titers in the infections of parainfluenza 3 virus and RS virus.

It is generally accepted that secretory antibodies play a very important role in the prevention of respiratory infections, but it is also considered that the circulating antibody level is a very significant indication of the establishment of infections. In parainfluenza 3 and RS virus infections, reinfections are very common but seem to depend more or less upon circulating antibody levels. There is a correlation between circulating antibody level and infection rate in parainfluenza 3 infection in some groups of school children in our observations of about one year. In the case of RS virus infection, observations were made in some nursery institutions and an experience in school children, in which also a circulating antibody level of some degree presents indications of infection rates.