>>12532946CORONAVIRUS
The Oxford-AstraZeneca vaccine is based on the virus’s genetic instructions for building the spike protein. But unlike the Pfizer-BioNTech and Moderna vaccines, which store the instructions in single-stranded RNA, the Oxford vaccine uses double-stranded DNA.
DNA Inside an Adenovirus
The researchers added the gene for the coronavirus spike protein to another virus called an adenovirus. Adenoviruses are common viruses that typically cause colds or flu-like symptoms. The Oxford-AstraZeneca team used a modified version of a chimpanzee adenovirus, known as ChAdOx1. It can enter cells, but it can’t replicate inside them.
DNA inside
an adenovirus
AZD1222 comes out of decades of research on adenovirus-based vaccines. In July, the first one was approved for general use — a vaccine for Ebola, made by Johnson & Johnson. Advanced clinical trials are underway for other diseases, including H.I.V. and Zika.
The Oxford-AstraZeneca vaccine for Covid-19 is more rugged than the mRNA vaccines from Pfizer and Moderna. DNA is not as fragile as RNA, and the adenovirus’s tough protein coat helps protect the genetic material inside. As a result, the Oxford vaccine doesn’t have to stay frozen. The vaccine is expected to last for at least six months when refrigerated at 38–46°F (2–8°C).
Entering a Cell
After the vaccine is injected into a person’s arm, the adenoviruses bump into cells and latch onto proteins on their surface. The cell engulfs the virus in a bubble and pulls it inside. Once inside, the adenovirus escapes from the bubble and travels to the nucleus, the chamber where the cell’s DNA is stored.
ADENOVIRUS
Entering
the cell
VACCINATED
CELL
Virus engulfed
in a bubble
Leaving the
bubble
Injecting
DNA
DNA
mRNA
mRNA
CELL
NUCLEUS
