# 5.5.1  Calculating quantities of vaccine for a particular supply period

The vaccine needs for a specific storage or supply period (in this case, 12 months or 48 working weeks) can be calculated using the following equation:

qperiod = (qyear ÷ 12) x psupply when the supply period is given in months, or qperiod = (qyear ÷ 48) x psupply when the supply period is given in working weeks. where:

• qperiod = vaccine needs for the period
• qyear = annual vaccine needs
• psupply = supply period (in months or weeks).

You can see an example of vaccine needs calculated in weeks in the following question.

• If the number of doses of vaccine required for one year in an imaginary kebele is 2,000, how many doses would be needed for a two-week period?

• In this example, the annual vaccine needs qyear = 2,000 and the supply period psupply is 2 weeks.

The vaccine needs for one week would be 2,000 doses ÷ 48 working weeks.

So the vaccine needs for the period (qperiod) of 2 weeks is (2,000 ÷ 48) x 2 = 83 doses.

Therefore, 83 doses would be required for a two-week period in this example.

5.5  Ordering vaccines

5.5.2  Calculating the minimum stock level