The prophylactic use of convalescent serum for the prevention of measles among children exposed to the disease has been reported by various investigators. The protective value of this agent seems unquestionable. The use of immune serum and whole blood from children or adults who have had an attack of the disease several years previously has also been advocated, but little evidence has been advanced as to the exact value of this agent.
During the last four months of the year 1928 and the early part of 1929, we had the opportunity to test the value of convalescent and immune adult serums, in various doses, among children in Porto Rico exposed to the disease by familial contact. One hundred and twenty doses of convalescent serum and 393 doses of immune adult serum were administered to more than 500 children, over 6 months and under 15 years of age, who had not