A stochastic model for competition between viral agents in the presence of interference. 1. Live virus vaccine in a randomly mixing population, Model 3.

Abstract

Previous reports have indicated the extreme difficulty of detecting the action of interference between wild viral agents in the field. There is evidence that the potential force of interference in relation to mass use of live virus vaccine is much greater. A stochastic epidemic model for competitive and interfering viral agents has been set up for a randomly mixing population of 400 persons. The model has been simulated on an IBM 7040 computer. The immunity status of the population and the vaccination schedule are flexible and are assigned by parameter cards. In the examples given, the wild agent is taken to be a Coxsackie B virus and the vacdne to be the Sabin live virus poliomyelitis vaccine. The effect of different vaccination schedules and of the proportion of the population susceptible to the vaccine virus is reported in terms of the estimated frequency distribution of the size of the resulting epidemics. The results of simulation of the model give quantitative summaries of the relative effect of the action of various factors as reflected in the distribution of the epidemic size. The restrictiveness of randomly mixing population models is discussed and plans for a community-of-families model are outlined.