Even as the World celebrates the positive news by Pfizer Inc and BioNTech SE on the effectiveness of the Covid-19 vaccine, it may not be coming to the local pharmacies for the general public any time soon.

The reason being the vaccine's complex and super-cold storage requirements.

On Monday, Pfizer Inc and BioNTech SE had announced the vaccine was 90 per cent effective in preventing Covid -19 infections in ongoing Phase - 3 trials. 

The main issue is that the vaccine, which is based on a novel technology that uses synthetic mRNA to activate the immune system against the virus, needs to be kept at minus 70 degrees Celsius (-94 F) or below.

That requirement will limit where the vaccine can be used. However, Moderna’s mRNA vaccine must be stored at -4 F (-20 C), which is not ideal, but not quite as challenging.  

Still, a vaccine that might be 90 per cent efficacious becomes more attractive - regardless of distribution challenges.

 Its said that even the most sophisticated hospitals in the United States will face problems in storage, leave alone in rural areas or poor countries where resources are tight.

'The cold chain is going to be one of the most challenging aspects of delivery of this vaccination,' said Amesh Adalja, senior scholar at Johns Hopkins Center for Health Security.

'This will be a challenge in all settings because hospitals even in big cities do not have storage facilities for a vaccine at that ultra-low temperature.'

Pfizer is working closely with the US government and state officials on how to ship the vaccine from its distribution centres in the United States, Germany and Belgium to around the globe. 

The detailed plan includes using dry ice to transport frozen vaccine vials by both air and land at their recommended temperatures for upto 10 days.

They can be kept in an ultra-low temperature freezer for up to six months, or for five days at 2-8 degrees Centigrade - a type of refrigeration commonly available at hospitals.

The Pfizer storage units can also be refilled with ice for up to 15 days.

But shots will spoil in around five days at normal refrigeration temperatures of slightly above freezing. The companies are analyzing if they can extend that for two weeks.

Other vaccines including ones from Johnson & Johnson and Novavax Inc can be stored at 2-8 degrees C, the temperature of a regular refrigerator.

It will be a challenge for the doctors to store vaccines in standard refrigerators and deploy all 975 doses in each Pfizer vaccine container in less than five days or restock them with dry ice and open them only twice a day to extend the vaccines' life span.

Vaccines must be stored and transported within the required temperature range of 2 degree Centigrade to 8 degree Centigrade at all times. Most vaccines are considered to be damaged at 0 degree Centigrade. Frozen or damaged vaccine may not visually appear solid or change in appearance.

(With inputs from Wion)

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