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Strengthening routine immunization services and sustainable financing for immunization

Q&A About Immunization - Archives

Question from a Medical Student:
What will be the exact consequences if the cold chain in immunization is broken?

Answer:
Maintaining most vaccines within a fairly narrow temperature range from the time of manufacture until the time of administration is first and foremost required to help ensure that the vaccine stimulates the desired immune response. Different types of vaccines have very different temperature requirements. If a vaccine is exposed to too high temperatures for too long, or if certain vaccines such as hepatitis B vaccine are frozen, they are not likely to be effective.

Vaccines damaged by exposure to temperatures that are too high or too low may affect the protection of the children vaccinated. They may also affect other people if the break in the cold chain leads to disease outbreaks. Public confidence in immunization will be harmed greatly if children vaccinated with ineffective vaccines get the disease, and there may be significant economic consequences if the cold chain is broken. For example, a refrigerator full of the more expensive combination vaccines can contain many thousands of dollars worth of vaccines that are lost. Administering previously-frozen DTP vaccines can also result in the development of sterile abscesses that cause unnecessary pain and further damage the reputation of an immunization program.

Vaccine vial monitors (VVM) and other monitors designed to alert health workers that there has been a cold chain break are widely available. In fact, they are now included with all heat-sensitive vaccines obtained through UNICEF. To determine if a vaccine has been frozen, most practitioners use a simple shake test that you can read more about in Immunization Essentials, pages 105-106.

For additional information on vaccine handling and the cold chain, see the following resources: