Vaccines are sensitive biological products. Some vaccines are sensitive to freezing, some to heat and others to light. Vaccine potency, meaning its ability to adequately protect the vaccinated patient, can diminish when the vaccine is exposed to inappropriate temperatures. Once lost, vaccine potency cannot be regained. To maintain quality, vaccines must be protected from temperature extremes. Vaccine quality is maintained using a cold chain that meets specific temperature requirements. Image shows recommended vaccine storage temperatures at each level of the cold chain. It is essential that all those who handle vaccines and diluents know the temperature sensitivities and the recommended storage temperatures for all the vaccines in the national schedule.
- Diluents should never be frozen.
- If diluents are packaged with the vaccine, the product should be stored at +2 °C to +8 °C.
- Bundled lyophilized-liquid combination vaccines should never be frozen and should be stored at +2 °C to +8 °C.
Sensitivity to heat and freezing
Image shows the relative heat sensitivity of vaccines. These vaccines are grouped into six categories. Within each of these six categories, the vaccines are arranged in alphabetical order, not in order of sensitivity to heat within the group. The most heat sensitive vaccines are in Group A and the least heat sensitive vaccines are in Group F. Note that the heat stability information shown for freeze-dried vaccines applies only to unopened vials; most freeze-dried vaccines rapidly lose potency after reconstitution. In addition, it is important to keep opened multi-dose vaccine vials that do not contain preservative – whether lyophilized or liquid – cooled at temperatures between +2 °C and +8 °C during the immunization session, or within six hours after opening, whichever comes first. Vaccines that are sensitive to freezing and should be protected from sub-zero temperatures are listed in below.
Freeze sensitive vaccines
DO NOT FREEZE THESE VACCINES!!!
• DTaP-hepatitis B-Hib-IPV (hexavalent)
• DTwP or DTwP-hepatitis B-Hib (pentavalent)
• Hepatitis B (Hep B)
• Hib (liquid)
• Human papillomavirus (HPV)
• Inactivated poliovirus (IPV)
• Rotavirus (liquid and freeze-dried)
• Tetanus, DT, Td
Sensitivity to light
Some vaccines are very sensitive to light and lose potency when exposed to it. Such vaccines should always be protected against sunlight or any strong artificial light, and exposure should be minimized. Vaccines that are as sensitive to light as they are to heat include BCG, measles, measles-rubella, measles-mumps-rubella and rubella. These vaccines are often supplied in dark glass vials that give them some protection from light damage; but they should be kept in their secondary packaging for as long as possible to protect them during storage and transportation.
Controlled Temperature Chain (CTC)
An increasing number of vaccines are being examined to determine their compatibility with a Controlled Temperature Chain (CTC), which would allow their use at ambient temperatures. WHO defines a CTC as the on-label use of a WHO-prequalified vaccine out of the traditional +2 °C to +8 °C cold chain for a limited period of time, at temperatures of up to 40 °C, just before administration. Vaccines licensed accordingly can be used in a CTC. The CTC approach can be adopted by countries for carefully chosen circumstances, such as for special strategies or mass vaccination campaigns.
Reference :- Module 2: The vaccine cold chain WHO
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