Immunization coverage targets
You now know how to calculate the annual vaccine needs for immunization of everyone in the target population. The EPI policy is to immunize 100% of the target population, but you may not be able to reach everyone in the target population in one year (for example, if your kebele includes very remote areas). Your annual action plan will include a percentage target from the woreda health office for the immunization coverage rate — the percentage of the eligible population that has been agreed as your objective for immunization with each of the EPI vaccines this year. The performance of your Health Post will be measured against this target.
If the annual target is less than 100% for a particular vaccine, you can estimate the number of vaccine doses you will actually need as follows. Start with the number of doses required to immunize everyone in the target population (i.e. total coverage), and multiply that number by the agreed (lower) percentage target for immunization coverage in your setting. We use the letters ‘ic’ to represent the percentage target for immunization coverage in calculations. Now look at the example in Table 5.3. (Your targets will be different.)
Table 5.3 Estimate of actual vaccine doses needed for various percentage targets for immunization coverage in an imaginary population of 5,000. (ic stands for immunization coverage target)
| Vaccine | Number of doses for 100% coverage | % coverage target (ic) | Actual number of doses needed |
|---|---|---|---|
| BCG (1 dose) | 200 | 90 | 180 |
| Polio (4 doses) | 800 | 90 | 720 |
| Pentavalent (3 doses) | 600 | 100 | 600 |
| PCV10 (3 doses) | 600 | 90 | 540 |
| Measles (1 dose) | 200 | 80 | 160 |
| Tetanus toxoid (2 doses) | 2,300 | 65 | 1,495 |
How many doses of TT vaccine would you need to immunize the eligible women in Table 5.3 with three doses per woman, if you increased the percentage coverage target to 70%?
Show answer
Total 100% coverage with three doses would require 3,450 doses. If the coverage target is 70%, the actual doses required would be 3,450 x 0.7 = 2,415 doses.
Note that you can use the same method of calculation to estimate the number of ampoules of specific diluents required to reconstitute the freeze-dried vaccines (BCG and measles), and your requirement for injection equipment.