Can we prevent the next epidemic? The elimination of childhood diseases by mass vaccination
by
Mick Roberts
AgResearch

A major epidemic occurs when there is a sufficient number of susceptible people in a population. Incomplete vaccination coverage during childhood results in a build-up of the unprotected community over time, hence (to a first approximation) vaccination does not change the size of an epidemic but it increases the inter-epidemic period.

Recently in New Zealand there have been outbreaks of measles and pertussis every six and five years respectively. A model has been used to compare the dynamics of these diseases, and to determine the optimum ages at which children should be vaccinated against them. Whereas measles could be eliminated by giving the second vaccination at five years instead of eleven, it is difficult to devise a practical scheme that would eliminate pertussis. It is then necessary to consider vaccination schemes in the light of the age-structure of future epidemics as well as their timing.

Date received: August 26, 1999