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Q&A About Immunization - Archives

Question from a post-graduate student in public health in India:
Hepatitis B is considered to be a freeze-sensitive vaccine. So when the temperature in the dial thermometer in domestic-type refrigerator (in the field) shows 0 degrees Celsius and hepatitis B vaccine has been placed at this temperature, has that hepatitis B vaccine lost the potency? If not what is the duration for which hepatitis B vaccine can be stored at 0 degrees Celsius without loosing the potency?

Response:
Hepatitis B vaccine can freeze when stored for an hour at -0.5 degrees Celsius, which results in a loss of its potency.

Health workers should be aware that different manufacturers' products may behave slightly differently from each other. Also, they should consider that dial thermometers may not be extremely precise, so the temperature may be a little higher or lower than 0 degrees when the thermometer reads 0 degrees. Moreover, unless one has a recording thermometer, one doesn't know what was the temperature at other times of the day; e.g., during the night or on weekends when nobody was looking at the thermometer. Finally, the temperature in different parts of the refrigerator is not uniform in any event and therefore may not correspond exactly to the temperature where the thermometer was placed.

Shake Test Diagram
Source: Immunization Essentials, p. 105

For all of these reasons, when you are concerned that hepatitis B vaccine may have frozen, it is advisable to use the "shake test," which determines if the vaccine looks like it might have frozen. This is described on page 105 of Immunization Essentials.

If you suspect that hepatitis B vaccine has been frozen, you should inform your supervisor and discard the vaccine. Adjust the refrigerator temperature appropriately and carefully monitor it.

Vials for hepatitis B vaccine from certain manufacturers come equipped with vaccine vial monitors (VVMs) that indicate exposure to heat, but VVMs do not give information about whether the vials have been exposed to freezing temperatures.