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The discussion in the previous slides (12-16) leads to the conclusion that the critical proportions of vaccination required to eradicate an infection (PC) can be calculated for specified infections in specified populations (from the average age at infection prior to vaccination (A) and life expectancy at birth (L) through the basic reproductive rate (R0)).

This slide presents approximate estimates of the order of magnitude of the critical proportions of vaccination (PC), derived from several studies.

For successful eradication, these levels of vaccination coverage should be achieved in all sectors or of the population; a national average is not enough, as the microorganism may be sustained in "pockets" of the population where R remains >=1.

MORE: Estimated values of A, L, R0 and PC for different infections and populations.

(Source of data: Fine P. Herd immunity: history, theory, practice. Epidemiol Rev 1993; 15:265-302.)