in the quest for safer vaccines , and in accordance with the recommendations of a who scientific group , a field trial was undertaken in western nigeria in may 1964 to make direct comparisons of the antigenicity and reaction rates of three further-attenuated measles vaccines ( schwarz , beckenham 20 and beckenham 20/2 ) and enders edmonston b vaccine plus gamma-globulin .
C0042211
attenuated
C0042210
vaccine