The AstraZeneca-Oxford vaccine (AZD1222) is a chimpanzee adenovirus-vectored vaccine. This means that the company took a virus that normally infects chimpanzees, and genetically modified it.
Adenovirus-vectored vaccines have been in development for a long time, in particular against malaria, HIV and Ebola. But no adenovirus vaccine has ever before been approved for use on humans in the USA. Some adenovirus vaccines in past trials have been simply ineffective, while others have been attacked by the body’s immune system (human adenoviruses can cause the common cold, so some people already have antibodies to these viruses).
AstraZeneca’s vaccine can be transported and stored at the same temperatures you might find in a normal refrigerator – between about 36° and 46° Fahrenheit for as long as six months.