The Cold Chain

Cold chain is the vital link in Immunization. However, potent a vaccine may be, if cold chain is not maintained from the source of vaccine manufacture to the site of vaccine administration -–the vaccine efficacy will grossly suffer. To maintain the potency of the vaccine a safe zone of temperature is mandatory.

The safe zone for vaccine storage for short term i.e. 1 to 2 months is + 2oC to + 8o C. For long term storage, - 20o C is preferred only for BCG, OPV and Measles/ MMR. Do not freeze other vaccines. Domestic refrigerators/ Ice lined refrigerators (ILR) are used for short term storage and deep freezer for long term storage. Vaccine carriers are used for carrying the vaccine to an outreach centre which maintain the ideal temperature of + 2o C to + 8o C with the help of 4 fully frozen ice packs contained in them. Cold boxes are used in fixed centres as alternative vaccine storage equipment in the event of short duration of electricity failure.

Dial Thermometers are used to monitor the ILR temperature and Alcohol stem thermometer for the deep freezer. The temperature monitoring should be done twice a day in the case of ILRs and deep freezer, 24 hours in the walk-in coolers where vaccines are stored in the regional stores for longer period. Currently Vaccine Vial Monitor (VVM) is also available for temperature monitoring.

The “T” Series of vaccines (vaccines containing the alphabet ‘T’ in there name) namely DPT, DT, TT, Typhoid Vi and also Hepatitis B vaccines should not be frozen. Once frozen the aluminium salts which are used as adjuvants will get desiccated and act as irritants which may result in sterile abscess. Hence, care should be taken not to allow these vaccines to come in direct contact with ice. It is mandatory that shake test is done before the use of either single or multidose vials of these vaccines to make sure that the solution is uniform. Generally, potency of the vaccine stored is tested by lifting a sample vial of OPV only. If this most thermolabile vaccine is found to be potent, the rest of the vaccines are presumed to be equally potent.

If you are storing vaccines in a domestic refrigerator, it should be used only for vaccine storage. You can keep OPV in the freezer compartment and the rest of the vaccines in the non-freezing lower compartments. No vaccine should be stored in the baffle tray or the door shelves. Repeated thawing of OPV should be avoided for all practical purposes. Never carry vaccines in a flask for an outreach place. All UIP vaccines are available free of cost from your local health authority.

You are allowed to collect your professional fees for the services rendered. However, utilization report should be submitted periodically. You can also send OPV vial for potency test with the help of your local Health Authority.

It is advisable and preferable to adopt a single day immunization practice in your clinic/nursing home especially when you are using the multidose vials to minimize the risk/s of contamination or potency loss. Alernatively two days a week strategy can be adopted so that the wastage of multidose vials could be avoided. Cold Chain for Vaccines

• The safe zone for vaccine storage + 2o C to + 8o C
• Do not freeze DPT, DT, TT, Typhoid Vi and HB vaccines
• Refrigerator/ ILR / Deep freezer used for vaccine storage
• Temperature Monitoring
• Vaccine Vial Monitor
• Potency test for OPV