Thawing process for the Pfizer-BioNTech COVID-19 vaccine
The Pfizer-BioNTech COVID-19 vaccine is unstable at refrigerated temperatures and must be stored frozen at ultra low temperature, and then transferred to a refrigerator or cold store to thaw before use. Further details can be found in our standard operating procedure for Unpacking of frozen COVID-19 Vaccine Pfizer-BioNTech and transfer to fridges to thaw in Trusts without freezers. Public Health England’s Immunisation Against Infectious Diseases (The Green Book) states that a 195 vial pack may take 3 hours to thaw in a refrigerator.
If a relatively large number of frozen vaccines are placed in a small refrigerator to thaw, it is possible that they may reduce the air temperature in the refrigerator sufficiently to bring it down below +2oC, or even down to or below 0oC in the whole or part of the refrigerator.
Placing frozen vaccines in the same refrigerator as defrosted vaccines risks potentially refreezing the defrosted vaccine or other vaccines stored in the refrigerator. Public Health England’s Immunisation Against Infectious Diseases (The Green Book) advises that defrosted or other vaccines should not be subjected to freezing temperatures. Freezing may cause deterioration of the vaccine, and may give rise to a loss of potency and an increase in reactogenicity. It may also cause hairline cracks in the glass ampoule/vial, allowing the contents to be contaminated.
Principles for defrosting the Pfizer-BioNTech COVID-19 vaccine
Thawing in a refrigerator
To ensure that thawing the frozen vaccine does not affect defrosted vaccines:
- If possible, use a dedicated refrigerator to thaw frozen vaccines. See our Institutional Readiness for Managing COVID-19 Vaccine Pfizer-BioNTech in Trusts for more information.
- Use a large refrigerator or cold store for thawing frozen vaccines if a dedicated refrigerator is not possible.
- Public Health England’s Immunisation Against Infectious Diseases (The Green Book) recommends running refrigerators as close to +5oC as possible to give more leeway for temperature reduction.
- If it is necessary to thaw frozen vaccines in a relatively small refrigerator with other vaccines, make sure the temperature probe is near the defrosted vaccines, not the frozen ones. Monitor regularly throughout the thawing process
Thawing at room temperature
It is preferable to thaw frozen vaccine in a refrigerator. However, Public Health England’s Immunisation Against Infectious Diseases (The Green Book; Chapter 14a) advises that individual frozen vials may be thawed for 30 minutes at temperatures up to 25°C for immediate use.
In this instance, the vial must be diluted within 2 hours of removing from the freezer and used within 6 hours of dilution.
- Clarification on expiry of vials defrosted at room temperature
- Section on "Thawing at room temperature" added. Link to best practice page added. Minor typographical changes to text.