Australia’s regulator says the Pfizer COVID-19 vaccine can now be kept at normal freezer temperatures for up to two weeks during transport and at regular fridge temperatures for up to five days.

Key points:

  • Messenger RNA inside the Pfizer vaccine is fragile, which is why it’s transported at sub-zero temperatures
  • Data from Pfizer shows the vaccine remains stable for short periods at warmer temperatures
  • The US and Europe have already approved transport at these temperatures

Previously, the vaccine needed to be kept at sub-zero temperatures of between -90C and -60C, making transportation logistically challenging.

The Therapeutic Goods Administration (TGA) announced the decision late last week.

“These changes will enable greater flexibility in storage, transport and deployment of the Pfizer COVID-19 vaccine across Australia,” the TGA said when approving the changes last Thursday.

It was the same day as Australia’s health advice changed to preference the Pfizer vaccine over AstraZeneca’s for a large portion of the country’s population.

Australia has secured another 20 million doses of Pfizer as the federal government overhauls its COVID-19 vaccination plans. RECAP: Look back on the latest news on the COVID-19 pandemic.

Pfizer’s mRNA technology

The Pfizer vaccine has been shown to be 95 per cent effective at preventing symptomatic COVID-19.

It uses messenger RNA (mRNA) encased in a lipid layer to train the body’s immune system to detect the spike protein of SARS-CoV-2 (the virus that causes COVID-19) and neutralise infection.

This mRNA is very fragile, which is why regulators previously said the vaccine needed to be kept at sub-zero temperatures at all times.

But in February, Pfizer submitted new data to the US Food and Drug Administration, which showed the vaccine remained stable for short periods at higher temperatures.

The US regulator then moved to allow undiluted frozen vials of the Pfizer vaccine to be transported and stored between -25C and -15C.

In March, the European Medicines Agency followed suit, approving storage of the Pfizer vaccine at domestic freezer temperatures.

Pfizer regulations in Australia

This change means that in Australia, unopened vials of the Pfizer vaccine can now be stored and moved at between -25C and -15C for up to two weeks.

Once they’ve been stored or transported at these domestic freezer temperatures, the vials must be returned to ultra-cold longer-term storage within the original shelf life of the vaccine.

Unopened vials can be stored for up to five days at domestic refrigerator temperatures: between 2C to 8C.

The Pfizer vaccine is diluted with saline after the vial is opened and before it is administered to a person.

The TGA says diluted vaccine, in either vials or syringes, can now be stored or transported at room temperatures of up to 30C for up to six hours.

For longer-term storage, the Pfizer vaccine must be kept at dry ice or ultra-cold temperatures of between -90C and -60C.