While an earlier live measles vaccine induced a high degree of immunity it also caused clinical reactions of variable severity in some vaccinated children. A number of attenuated measles vaccine strains have been developed to avoid these problems, and this paper reports the results of small-scale trials with 3 attenuated measles vaccines and a new further-attenuated vaccine on children from 9 months to over 4 years old.All 4 vaccines produced a satisfactory serological response. The new further-attenuated vaccine (Moraten) produced less fever and fewer rashes in the vaccinated children than the other vaccines which had been extensively tested by other workers. The incidence of severe reactions and complications was low with all vaccines.
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