5.2.2  Calculating numbers in the target population

Table 5.1 (on the next page) shows an estimate of the target population for immunization in a kebele with a total population of 5,000. A figure of 4% of the Ethiopian population is usually taken to estimate the coverage required for all live births and surviving infants. You can assume that (on average) about 23% of the Ethiopian population will be women of childbearing age, of whom about 4% will be pregnant in a typical year.

You estimate the target population by multiplying the total population by the percentage in a particular category; for example in Table 5.1:

Expressing a percentage as a decimal number is easy, e.g. 90% is the same as 0.9; 23% is the same as 0.23, and 4% is the same as 0.04.

• The estimated number of women eligible for TT vaccination (Figure 5.3) is 5,000 x 23% (or 0.23) = 1,150
• The estimated number of children eligible for all other EPI vaccines is 5,000 x 4% (or 0.04) = 200, if you take the simple average of 4%. If you use the Ministry of Health indicators of live births (3.6%) and surviving infants (3.4%), the numbers will be 170 and 180 respectively.

Figure 5.3  About 23% of the Ethiopian population are women of childbearing age (pregnant and non-pregnant combined). (Photo: Ali Wyllie)