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.

Table 5.1  Estimating the target population (pt) for immunization in a kebele with a total population of 5,000.
Category% of total populationEstimated number in target population
Live births3.6180
Surviving infants3.4170
Women of childbearing age (pregnant and non-pregnant)231,150

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)
  • Look back at Figure 5.2. What was the estimated target population eligible for TT immunization in Fura kebele in the year shown?

  • The estimated eligible population for TT vaccination was 1,478 women of childbearing age (247 pregnant and 1,231 non-pregnant) in Fura that year; this is 23% of the total population of 6,348 in the kebele.

5.2  Estimating vaccine needs based on the size of the target population

5.2.3  Calculating required doses based on the immunization schedule