5.2.6 Calculating annual vaccine needs from the size of the target population
To calculate the annual vaccine needs for your immunization programme from the size of the target population, you need to multiply together the four values explained in Sections 5.2.1 to 5.2.4 of this study session. The calculation can be summarised using the equation shown below:
- Annual vaccine needs = pt x dn x ic x wf
The equation uses the following values:
- target population (pt)
- number of doses in the schedule (dn)
- target immunization coverage (ic) expressed as a decimal number (not a percentage)
- wastage factor (wf).
Calculate the annual vaccine needs for pentavalent vaccine for a target population of 200 surviving infants, using the equation given above. Remember that three doses of this vaccine per child are needed for full immunization. Assume the target coverage rate is 90% and the wastage factor is 1.33 in this example.
The calculation is as follows:
- number of surviving infants (pt) = 200
- number of pentavalent doses in the EPI schedule (dn) = 3
- target coverage rate (ic) expressed as a decimal number = 0.9 (90%)
- wastage factor (wf) = 1.33
Annual pentavalent vaccine needs = pt x dn x ic x wf = 200 x 3 x 0.9 x 1.33 = 178
In this example, 718 doses of pentavalent vaccine would be needed annually. Remember that the requirement in your own kebele may be different.
Now we turn to the second method of calculating vaccine needs.