The Comirnaty vaccine by Pfizer who have partnered with BioNTech and the Moderna vaccine, unlike AstraZeneca which contains a viral vector, reportedly the common cold virus, are said to be pioneers of a new mRNA vaccine. MRNA vaccines were being produced and tested before the pandemic. Covid mRNA vaccines were reportedly being produced in March, as soon as the genetic structure of the virus was established. The idea is to replicate the covid antigen via genetic instructions. Once produced in the body it is recognised by the immune system which prepares it for the real thing. Reportedly Astra Zeneca has conditional marketing authorisation due to lack of data.
Messenger RNA vaccines are now being used in some cancer treatments. Described as a type of immunotherapy, an RNA sequence for mutant proteins specific to the cancer are injected, hopefully creating an immune response.