Litter-Mate Assays of Pertussis Vaccine

Abstract

Summary A series of comparative assays of two pertussis vaccines was carried out by the mouse intracerebral method, using litter-mates and placing one member of each litter on each dose. A statistical analysis of the results by the method described by Irwin (1950, p. 231), was carried out, making due allowance for the use of litter-mates. A slight increase of accuracy was found in five out of six assays, but this did not reach the 5% level of significance. Any real increase of accuracy must have been small. The results show that, as far as these tests are concerned, there is no advantage in the use of litter-mates, particularly when one takes account of the large amount of additional work necessary in the animal house.