# Situation: A nurse manages the National Immunization Program (NIP) at a Rural Health Unit (RHU) that serves 12 barangays. The nurse combines last year's data from two of the barangays: Barangay 1: 150 eligible infants; 140 received pentavalent 1; 126 received pentavalent 3 Barangay 2: 110 eligible infants; 100 received pentavalent 1; 78 received pentavalent 3 What was the combined pentavalent 1-to-3 dropout rate for the two barangays? Round off to one decimal place.

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=627255  
> language: ko  
> subject: Nursing Practice I — Community Health Nursing

## 문제

Situation: A nurse manages the National Immunization Program (NIP) at a Rural Health Unit (RHU) that serves 12 barangays.

The nurse combines last year's data from two of the barangays:
Barangay 1: 150 eligible infants; 140 received pentavalent 1; 126 received pentavalent 3
Barangay 2: 110 eligible infants; 100 received pentavalent 1; 78 received pentavalent 3
What was the combined pentavalent 1-to-3 dropout rate for the two barangays? Round off to one decimal place.

## 보기

1. 13.8%
2. 15.0% **✔ 정답**
3. 16.0%
4. 17.6%

**정답: 2**

## 해설

Dropout rate = (pentavalent 1 − pentavalent 3) ÷ pentavalent 1 × 100. Pool the counts first: pentavalent 1 = 140 + 100 = 240 and pentavalent 3 = 126 + 78 = 204, so (240 − 204) ÷ 240 × 100 = 36 ÷ 240 × 100 = 15.0%. The denominator is the number who started the series, not the eligible population, and the two barangay rates (10.0% and 22.0%) cannot simply be averaged because the barangays have different numbers of infants.

## 심화 해설

The question asks for a combined pentavalent 1-to-3 dropout rate across two barangays. The dropout rate measures the proportion of children who received the first dose but failed to complete the third dose. This is a core program indicator in the National Immunization Program because it reveals retention gaps that coverage alone can hide [1][3].

Step 1 — Combine the numerators and denominators first

Pooling data before calculating is required because the two barangays contribute different numbers of children. The formula is:

Dropout rate = (Pentavalent 1 − Pentavalent 3) ÷ Pentavalent 1 × 100

Combined pentavalent 1: 140 + 100 = 240

Combined pentavalent 3: 126 + 78 = 204

Dropouts = 240 − 204 = 36

Dropout rate = 36 ÷ 240 × 100 = 15.0%

Key point! The denominator is the number who received pentavalent 1, not the eligible population. Using eligible infants (260) would incorrectly produce 13.8%, which is option 1.

Step 2 — Why not average the two barangay rates?

Barangay 1 dropout rate = (140 − 126) ÷ 140 × 100 = 10.0%

Barangay 2 dropout rate = (100 − 78) ÷ 100 × 100 = 22.0%

Simple average = (10.0% + 22.0%) ÷ 2 = 16.0%, which is option 3.

This is incorrect because barangays have unequal cohort sizes. Barangay 1 contributes more children to the combined pool, so its lower dropout rate carries more weight. The pooled calculation automatically applies this weighting.

Watch out! Averaging percentages without considering the underlying population sizes is a common error in program monitoring. Always return to raw counts before combining rates.

Clinical and programmatic meaning

Pentavalent vaccine protects against diphtheria, pertussis, tetanus, hepatitis B, and Haemophilus influenzae type b. A child is classified as a dropout when the first dose is received but the third dose is not [1]. High dropout indicates that children start the series but do not complete it, leaving them only partially protected.

In Tanzania, first-dose coverage was approximately 97% while third-dose coverage was only 89%, demonstrating that dropout can persist even when initial uptake is strong [1]. Ethiopia similarly reports that individual vaccine coverage may improve while the proportion of fully vaccinated children remains low, highlighting dropout as a distinct barrier to full protection . Interventions such as text message reminders and sticker prompts have been evaluated specifically to reduce dropout, confirming that retention—not just initial access—is an actionable program target [3].

A combined dropout rate of 15.0% means that for every 100 infants who began the pentavalent series, 15 did not receive the third dose. The nurse managing the RHU should investigate reasons for dropout—such as caregiver mobility, vaccine stockouts, or missed appointment tracking—and implement recall strategies for children who received pentavalent 1 but are overdue for pentavalent 3 [3].

| Calculation approach | Formula | Result | Interpretation |
| --- | --- | --- | --- |
| Pooled counts (correct) | (240 − 204) ÷ 240 × 100 | 15.0% | Weighted by actual cohort size |
| Simple average of barangay rates (incorrect) | (10.0% + 22.0%) ÷ 2 | 16.0% | Ignores unequal population sizes |
| Using eligible infants as denominator (incorrect) | (260 − 204) ÷ 260 × 100 | 21.5% | Mixes non-starters into the dropout measure |

The denominator for dropout must always be the number who received the first dose, because dropout is defined as failure to progress from dose 1 to dose 3 among those who started [1]. Children who never received any dose are a separate access problem, not a dropout problem.References (research sources)

- [1]Associated factors for dropout of first versus third doses of pentavalent vaccination in Tanzania.Research articleTillya R, Abdallah G, Msuya H, Bajaria S, Mtenga S, Festo C (2025) · DOI: 10.1016/j.vaccine.2025.126962

- [3]Reducing routine vaccination dropout rates: evaluating two interventions in three Kenyan districts, 2014.Research articleHaji A, Lowther S, Ngan'ga Z, Gura Z, Tabu C, Sandhu H (2016) · DOI: 10.1186/s12889-016-2823-5

## 임상 시나리오

Pentavalent Dropout Rate CalculationPool data before computing combined rates
Always pool numerators and denominators across barangays before calculating. Combined pentavalent 1 = 240, pentavalent 3 = 204, so dropout rate = (240 - 204) / 240 x 100 = 15.0%.

The denominator is pentavalent 1 recipients, not eligible infants. Using 260 eligible infants gives 13.8%, which is incorrect.

Do not average barangay rates (10.0% and 22.0%) because unequal cohort sizes require weighted pooling.

CautionA high dropout rate signals retention gaps. Investigate why children who received dose 1 did not return for dose 3, and trace defaulters at the RHU level.

```

## 핵심 개념

- **Dropout rate** — Proportion of children who started a vaccine series but did not complete it, calculated as (first dose - last dose)/first dose x 100.
- **Pentavalent vaccine** — Combination vaccine protecting against diphtheria, tetanus, pertussis, hepatitis B, and Haemophilus influenzae type b.
- **Pooled data** — Combining counts from multiple reporting units before calculating rates to properly weight different cohort sizes.
- **Eligible population** — Infants who should receive the vaccine based on age criteria, not necessarily those who started the series.
- **National Immunization Program (NIP)** — Public health program ensuring access to vaccines for vaccine-preventable diseases across all local government units.

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