Which vaccine can be frozen?

NORCET 1 - 2020

Pharmacology

Easy

Appeared in: NORCET 1 - 2020

Explanation

The Oral Polio Vaccine (OPV) is the most heat-sensitive vaccine in the immunization schedule.
To preserve its potency, OPV is stored at sub-zero temperatures, typically between minus 15°C and minus 25°C in deep freezers or walk-in freezers at regional and district levels.
Freezing does not harm the OPV; in fact, it is the standard procedure for its long-term storage.
Even in a standard refrigerator at a health center, OPV is often kept in the freezer compartment.

Option A: BCG is a freeze-dried vaccine. While the powder itself is stable, the diluent it is reconstituted with must never be frozen. The reconstituted vaccine is also sensitive to heat and light. Standard storage is in a refrigerator between +2°C and +8°C.
Option C: MMR, like BCG, is a freeze-dried vaccine. It is stored in the refrigerator between +2°C and +8°C. The diluent must not be frozen. Freezing is not the recommended storage method.
Option D: DPT and DT vaccines are freeze-sensitive. They contain an aluminum salt as an adjuvant. If frozen, the adjuvant clumps together, which irreversibly destroys the vaccine's effectiveness and can lead to sterile abscesses if administered. These vaccines must be stored between +2°C and +8°C and protected from freezing.

Visual 1: Diagram - A diagram of a vaccine refrigerator showing the correct placement of different vaccine types. OPV is in the freezer, while DPT, BCG, and MMR are on the shelves of the refrigerator compartment, away from the freezing unit.
Visual 2: Infographic - An infographic illustrating the 'Shake Test' used to determine if freeze-sensitive vaccines like DPT have been accidentally frozen and damaged.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Vaccine storage and cold chain management as background academic context rather than a clinical decision trigger.
A nurse's primary responsibility is to maintain the vaccine cold chain. Failure to do so results in administering a non-potent vaccine, leading to a false sense of security and leaving the patient unprotected.
Always check the Vaccine Vial Monitor (VVM) on OPV vials to assess cumulative heat exposure. The inner square must be lighter than the outer circle.
What if? If a vial of DPT vaccine is suspected to have been frozen (e.g., found at the back of the fridge near the cooling element), the nurse must not use it. The vial should be quarantined and a 'Shake Test' performed against a control vial from the same batch to confirm damage before it is discarded according to protocol.

How to Approach the Question

First, identify the core of the question, which is about the temperature sensitivity of vaccines, specifically which one can tolerate freezing.
Recall the two main categories of vaccine sensitivity: heat-sensitive and freeze-sensitive.
Remember that Oral Polio Vaccine (OPV) is the most heat-sensitive and is therefore stored frozen to maintain its potency.
Recall that vaccines containing an adjuvant (like DPT, DT, TT, Hep B) are freeze-sensitive and are destroyed by freezing.
Consider the freeze-dried vaccines (BCG, MMR). While the powder is stable, their diluents cannot be frozen, and their standard storage is refrigeration.
Based on this classification, identify Polio (OPV) as the vaccine that is routinely frozen and eliminate the other options.

Concept Tested & Keywords

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