The pfizer vaccine is mRNA, so when it goes into a cell it will use the translation machinery to convert to protein and that gets presented to the immune system

The pfizer vaccine is mRNA, so when it goes into a cell it will use the translation machinery to convert to protein and that gets presented to the immune system. The Oxford vaccine uses a non-reproductive adenovirus to introduce the RNA into the cell, with a similar result. I think the Oxford one won't have issues with storage. There are others that use recombinant protein from the virus.