In the WHO recommended EPI cluster sampling for assessing primary immunization coverage, the age group of children to be surveyed is
First, I need to recall what EPI stands for. It's the Expanded Programme on Immunization. Cluster sampling in this context is a method used to estimate immunization coverage in a population. The key here is knowing the specific age group targeted for this survey.
I remember that for primary immunization coverage, the focus is usually on children who have completed their initial series of vaccines. The primary series typically starts at birth and includes doses given at 6 weeks, 10 weeks, and 14 weeks, which are part of the DPT (diphtheria, pertussis, tetanus) and other vaccines like OPV (oral polio vaccine) and PCV (pneumococcal conjugate vaccine). So the age group would be around 12-23 months. This is because by 12 months, the child would have received the first three doses if they are on schedule, and 23 months is before the second birthday when some vaccines are given. This age range ensures that the children have had time to complete the primary series but are not yet due for booster doses, making it a good indicator of the primary coverage.
Now, looking at the options provided (even though they're not listed here), the correct answer should be 12-23 months. The other options might include younger or older age groups. For example, infants under 6 months might not have completed their primary series yet, and children over 24 months might have received booster shots, which could skew the data. The WHO recommends cluster sampling in this age group because it's the most accurate for assessing primary coverage without including boosters or excluding those who haven't started.
I should also consider why other age groups are incorrect. For instance, if an option was 0-11 months, they haven't completed the primary series. If it's 24-35 months, they might have had boosters. The key is the timing of the primary series completion, which aligns with 12-23 months.
A clinical pearl here is that the WHO uses cluster sampling in this age group because it's the standard for measuring primary immunization coverage, ensuring that the data reflects the effectiveness of the initial vaccination schedule without the influence of subsequent boosters. This is crucial for public health planning and evaluating vaccine programs.
**Core Concept**
The WHO Expanded Programme on Immunization (EPI) uses cluster sampling to estimate primary immunization coverage. The target age group is critical to ensure children have completed their primary vaccine series but not yet received booster doses.
**Why the Correct Answer is Right**
The correct age group is **12–23 months**. By this age, children should have received all primary doses (e.g., 3 doses of DPT, OPV, and PCV) as per the standard 6-week, 10-week, and 14-week schedule. Assessing this cohort avoids confounding from booster vaccines (e.g., DPT-4 at 18 months) and ensures accurate coverage metrics for the initial immunization phase.
**Why Each Wrong Option is Incorrect**
**Option A:** 0–5 months – Inf