The Pfizer vaccine on the other hand has to be stored at minus 70C (minus 94F) and is only stable for a short period at higher temperatures, making it difficult to administer away from hospital hubs. The Moderna jab can be stored for about 30 days before use. Read More Related Articles Read More Related Articles – How does the vaccine work? The Moderna jab is a messenger RNA (mRNA) vaccine. Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus's genetic code. An mRNA vaccine is injected into the body, where it enters cells and tells them to create antigens. These antigens are recognised by the immune system and prepare it to fight coronavirus. No actual virus is needed to create an mRNA vaccine. This means the rate at which the vaccine can be produced is accelerated. – Is the vaccine safe? Moderna said the vaccine was generally well tolerated, with no serious safety concerns identified.