Self-Assessment Questions (SAQs) for Study Session 5

Answer

The equation for calculating the annual vaccine needs, based on the size of the target population, is:

• Annual vaccine needs = pt x dn x ic x wf where:

• pt is the target population – for pentavalent vaccine this is the number of children aged 0–11 months (calculated below)
• dn is the number of doses of vaccine in the recommended schedule — this is 3 for pentavalent vaccine
• ic is the target immunization coverage rate — in this example it is 90%
• wf is the wastage factor (calculated below)

The number of children aged between 0–11 months is 5% (0.05) of the total population of 5,700, which is:

• 5,700 x 0.05 = 285 children in this age group (5% expressed as a decimal number is 0.05)

The wastage factor is calculated from the wastage rate of 5% using the equation:

• Wastage factor (wf) = 100 ÷ (100 – % wastage rate)

So for a wastage rate of 5%:

• wf = 100 ÷ (100 – 5) = 100 ÷ 95 = 1.05

Using the equation below to calculate the annual vaccine needs based on the target population size:

• pt x dn x ic x wf = 285 x 3 x 0.9 x 1.05 = 808 doses

So the annual pentavalent vaccine needs, based on the size of the target population in this kebele, is 808 doses.

Answer

The equation for calculating annual vaccine needs based on the size of the immunization sessions is as follows:

• Annual vaccine needs = posts x weeks x sessions x vials x doses; where (for PCV10 vaccine in this example):

• posts is the number of immunization sites, which is 1
• weeks is how many weeks the immunization site operates, which is 45
• sessions is the number of sessions per week, which is 2
• vials is the number of vials used per session, which is 5
• doses is the number of doses per vial, which is 2.

So the annual vaccine needs for DPT in this example is:

• 1 x 45 x 2 x 5 x 2 = 900 doses.

Answer

The wastage factor is calculated from the wastage rate (expressed as a percentage), using the following equation:

• Wastage factor (wf) = 100 ÷ (100 – % wastage rate)

In this example, the wastage rate for OPV has been set at 10%. So the wastage factor is:

• wf = 100 ÷ (100 – 10) = 100 ÷ 90 = 1.11

Therefore, the wastage factor is 1.11.

Answer

• a.In the example given in SAQ 5.2, there are two immunization sessions per week. Five multi-dose vials of PCV10 each containing 2 doses is used per session, so 20 doses are needed per week. Therefore the number of doses required for a 2-week supply period in this kebele is 40 doses.
• b.The minimum stock level is generally taken to be 25% (or 0.25) of the requirement for the supply period, which in this example is 2 weeks. The equation needed to calculate the minimum stock level for a 2-week period is:
  • s_mini = q_period x 0.25 (25% expressed as a decimal number is 0.25)
  • where q_period is the number of doses required for the supply period, which in this example is 40 doses.
  • s_mini = 40 x 0.25 = 10 doses.
  • So the minimum stock level for PCV10 vaccine for a 2-week period in this kebele is 10 doses.
• c. The maximum stock level for PCV10 for a 2-week period in this kebele is calculated from the following equation:
  • s_maxi = q_period + s_mini s_maxi = 40 + 10 = 50 doses
• d.So the maximum stock level for PCV10 vaccine for a 2-week period in this kebele is 50 doses.