# Situation: The public health nurse of a Rural Health Unit (RHU) holds a monthly immunization session at a Barangay Health Station (BHS) under the National Immunization Program (NIP). The nurse reconstitutes the bacille Calmette-Guérin (BCG) vaccine with its own diluent at the start of the session. At the latest, when must the reconstituted vial be discarded, if the session has not yet ended?

> source: MyMerci (mymerci.kr)  
> url: https://mymerci.kr/pages/nclex_q.php?qn_id=629526  
> language: ko  
> subject: Nursing Practice II — Maternal and Child Health Nursing

## 문제

Situation: The public health nurse of a Rural Health Unit (RHU) holds a monthly immunization session at a Barangay Health Station (BHS) under the National Immunization Program (NIP).

The nurse reconstitutes the bacille Calmette-Guérin (BCG) vaccine with its own diluent at the start of the session. At the latest, when must the reconstituted vial be discarded, if the session has not yet ended?

## 보기

1. 1 hour after reconstitution
2. 6 hours after reconstitution **✔ 정답**
3. 24 hours after reconstitution
4. 4 hours after reconstitution

**정답: 2**

## 해설

Reconstituted BCG and measles-containing vaccines contain no preservative. They are discarded 6 hours after reconstitution or at the end of the session, whichever comes first, and are kept cold and protected from light while in use.

## 심화 해설

The correct answer is 6 hours after reconstitution.

BCG is a live, attenuated bacterial vaccine supplied as a lyophilized powder that must be reconstituted with its specific diluent immediately before use. Once reconstituted, the vaccine becomes fragile because it contains no preservative to inhibit microbial growth or stabilize the live bacilli. This is the central reason for the strict discard time.

Reconstituted BCG must be discarded 6 hours after reconstitution or at the end of the immunization session, whichever comes first. The 6-hour limit is not arbitrary: beyond this window, the viability of the live Mycobacterium bovis bacilli declines, and the risk of bacterial contamination increases because the diluent provides a medium for growth. The vaccine must also be kept cold (2–8°C) and protected from light during the entire 6-hour use period, since both heat and ultraviolet light accelerate loss of potency in live vaccines.

The same 6-hour discard rule applies to measles-containing vaccines (measles, MR, MMR), which are also live, attenuated, and preservative-free after reconstitution. This shared rule is a high-yield comparison point for licensure examinations.

Watch out! Do not confuse the 6-hour rule for BCG and measles-containing vaccines with the longer discard times for other reconstituted vaccines. For example, some inactivated or subunit vaccines may be used for up to 6 hours or longer depending on the manufacturer, but the NIP standard for BCG and measles-containing vaccines is specifically 6 hours or end of session, whichever comes first.

Key point! The phrase "whichever comes first" means that if the session ends only 2 hours after reconstitution, the vial is discarded at that time, not held until the full 6 hours have elapsed. This prevents using a partially used vial at a later session when cold chain integrity and sterility can no longer be guaranteed.

| Vaccine type | Preservative after reconstitution | Discard time after reconstitution | Storage during use |
| --- | --- | --- | --- |
| BCG (live, attenuated) | None | 6 hours or end of session, whichever comes first | 2–8°C, protected from light |
| Measles-containing (live, attenuated) | None | 6 hours or end of session, whichever comes first | 2–8°C, protected from light |
| Other reconstituted vaccines (e.g., some inactivated) | Varies by product | Follow manufacturer or NIP guidance | Per product instructions |

The practical consequence of this rule is significant for outreach immunization sessions. Because a 20-dose BCG vial cannot be stored once opened, health workers often wait until enough infants are present before reconstituting a vial to avoid wastage. This practice, while economically rational, can delay timely vaccination if the threshold number of infants is not reached [1]. The 6-hour window therefore represents a balance between maintaining vaccine potency and minimizing unnecessary wastage in field settings.

Cold chain management studies reinforce that health workers must understand these time limits as part of overall vaccine quality control. Knowledge of correct reconstitution, storage temperature, and discard times directly affects whether the vaccine delivered to a child is still potent and safe . A vaccine that has been reconstituted beyond 6 hours may look unchanged, but its immunogenicity is no longer reliable, and it must not be administered.

The 1-hour, 4-hour, and 24-hour options are incorrect because they do not match the NIP standard for preservative-free live vaccines. The 24-hour option is particularly dangerous because it would allow significant bacterial growth and loss of live bacilli viability, potentially leading to both ineffective immunization and injection-site complications.References (research sources)

- [1]The real-life number of neonatal doses of Bacille Calmette-Guérin vaccine in a 20-dose vial.Research articleSchaltz-Buchholzer F, Frankel HN, Benn CS (2017) · DOI: 10.1080/16549716.2017.1267964

## 임상 시나리오

BCG Reconstitution: Discard TimePreservative-free live vaccine handling in immunization sessions
Reconstituted BCG must be discarded 6 hours after reconstitution or at the end of the session, whichever comes first. The same rule applies to measles-containing vaccines.

During the use period, keep the reconstituted vial cold at 2–8°C and protected from light to preserve live bacilli viability.

CautionDo not confuse this with longer discard times for other vaccines. BCG and measles-containing vaccines have no preservative, so the 6-hour limit is strict even if the session continues.

## 핵심 개념

- **BCG vaccine** — Live attenuated bacterial vaccine against tuberculosis, supplied as lyophilized powder requiring reconstitution.
- **Reconstitution** — Process of mixing a lyophilized vaccine with its specific diluent to prepare it for administration.
- **Preservative-free vaccine** — Vaccine lacking antimicrobial preservatives, making it vulnerable to contamination after reconstitution.
- **Cold chain** — System of storing and transporting vaccines at recommended temperatures, typically 2–8°C, to maintain potency.
- **National Immunization Program** — Public health program providing routine vaccines to eligible populations, including BCG at birth or first contact.

## 같은 주제 문제

- [Situation: A nurse from the Rural Health Unit (RHU) makes postnatal home visits to healthy…](https://mymerci.kr/pages/nclex_q.php?qn_id=629426)
- [Situation: A nurse from the Rural Health Unit (RHU) makes postnatal home visits to healthy…](https://mymerci.kr/pages/nclex_q.php?qn_id=629427)
- [Situation: A nurse from the Rural Health Unit (RHU) makes postnatal home visits to healthy…](https://mymerci.kr/pages/nclex_q.php?qn_id=629428)
- [Situation: A nurse from the Rural Health Unit (RHU) makes postnatal home visits to healthy…](https://mymerci.kr/pages/nclex_q.php?qn_id=629429)
- [Situation: A nurse from the Rural Health Unit (RHU) makes postnatal home visits to healthy…](https://mymerci.kr/pages/nclex_q.php?qn_id=629430)
- [Situation: The nurse holds a weekly well-baby clinic at a Barangay Health Station (BHS) fo…](https://mymerci.kr/pages/nclex_q.php?qn_id=629431)
- [Situation: The nurse holds a weekly well-baby clinic at a Barangay Health Station (BHS) fo…](https://mymerci.kr/pages/nclex_q.php?qn_id=629432)
- [Situation: The nurse holds a weekly well-baby clinic at a Barangay Health Station (BHS) fo…](https://mymerci.kr/pages/nclex_q.php?qn_id=629433)

---

More free questions: [기출문제](https://mymerci.kr/)

_학습 참고용입니다. 실제 임상은 최신 지침과 소속 기관 프로토콜을 따르세요._