Cold Chain and AEFI Nursing
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Direct answer
The cold chain is the system that keeps vaccines potent by holding them between 2 and 8°C from manufacturer to child, and the nurse is its custodian at the last and most fragile link. Heat-sensitive vaccines such as OPV and measles tolerate warmth worst, while aluminium-adjuvanted vaccines — DPT, TT and hepatitis B — are damaged by freezing, screened by the shake test and tracked by the vaccine vial monitor whose discard point is a darkened square matching the circle. An adverse event following immunisation ranges from expected fever and local pain to rare anaphylaxis, treated with intramuscular adrenaline into the anterolateral thigh; serious events — death, hospitalisation, disability or clusters — are reported within 24 hours.
What you must remember
- The chain holds 2 to 8°C; domestic refrigerators are never used.
- Equipment: the ice-lined refrigerator maintains 2 to 8°C with holdover through power cuts and stores most vaccines; the deep freezer at minus 15 to minus 25°C stores OPV, measles-group vaccines and diluents awaiting use; vaccine carriers with conditioned ice packs serve outreach.
- Heat sensitivity ladder: OPV is most heat-sensitive, followed by measles; freeze sensitivity marks hepatitis B, DPT and TT — freezing destroys the adjuvant and raises reaction rates.
- The shake test settles suspected freezing: a control vial frozen and thawed is shaken alongside the suspect; if the suspect's sediment settles in fine grains and resuspends poorly compared with the control, it was frozen and is discarded.
- Open vial policy: opened liquid multi-dose vials of DPT, TT, hepatitis B and OPV meeting storage criteria may be used in subsequent sessions up to four weeks; reconstituted BCG, measles and similar vaccines are discarded at the session's end or within four hours, never carried over.
- Minor AEFI — fever, pain, swelling within 48 hours — are managed with paracetamol weight-dosed, cold compress and counselling; serious AEFI (death, hospitalisation, disability, cluster) are reported within 24 hours on the prescribed form.
- Anaphylaxis at a session: adrenaline 1 in 1000, 0.01 mg per kg up to 0.5 mg intramuscularly into the anterolateral thigh, repeatable in 5 to 10 minutes; every session site keeps an equipped tray, and recipients are observed for 15 to 20 minutes.
- True contraindications are few: anaphylaxis to a previous dose or component, encephalopathy within 7 days of pertussis vaccination (later doses withheld, DT substituted), and significant immunocompromise avoiding live vaccines such as BCG, measles and OPV. Mild illness is never a contraindication.
Running one outreach session
The ANM plans a village session for sixteen children. The previous evening she conditions the ice packs (shaken to slush, so vaccines cannot freeze against hard ice), packs the carrier with vaccines, diluents beside them, VVMs checked, and signs the temperature log. At the session she checks VVMs again, reconstitutes BCG and measles with matched diluents, labels each reconstituted vial with time, and sets a four-hour discard discipline whatever doses remain. Liquid DPT and hepatitis B vials opened today are returned marked with the opening date, usable up to four weeks under the open vial policy — leftover reconstituted BCG goes to the discard pot at noon. A toddler with evening fever and thigh tenderness is managed as a minor AEFI — counselling and weight-based paracetamol. Had that child developed urticaria with wheeze instead, the drill is adrenaline 1 in 1000 into the anterolateral thigh at 0.01 mg per kg (capped at 0.5 mg), airway positioning and referral — the tray checked before the first injection precisely for this. The register, VVM discards and returns are reconciled the same day — cold-chain integrity is written documentation.
Where students slip
The sensitivity directions are swapped — OPV leads heat sensitivity while hepatitis B is the freeze-sensitive one — and the VVM's discard point is described as "any colour change", though early stages remain usable. The open vial policy is overextended to reconstituted vaccines, never carried beyond the session, and VVM status outranks the expiry date. In AEFI items, mild fever or a runny nose is not a contraindication; the true ones are narrow and specific. The adrenaline dose and site (anterolateral thigh in infants) is the discriminating detail.
Frequently asked questions
At what temperature range are vaccines stored?
Between 2 and 8°C throughout the cold chain, with OPV and measles-group vaccines also held frozen at minus 15 to minus 25°C in deep freezers until distribution.
What does the vaccine vial monitor show?
Cumulative heat exposure — the vaccine is discarded once the inner square darkens to match the outer circle, even if the expiry date has not passed.
What events are reportable as serious AEFI, and how soon?
Death, hospitalisation, life-threatening illness, disability and unusual or clustered events — reported within 24 hours on the prescribed reporting form.
How is anaphylaxis after vaccination treated?
Adrenaline 1 in 1000 at 0.01 mg per kg (maximum 0.5 mg) intramuscularly into the anterolateral thigh, repeated after 5 to 10 minutes if needed, with airway support and referral.