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How the Oxford-AstraZeneca Vaccine Works

How the Oxford-AstraZeneca Vaccine Works

The University of Oxford partnered with the British-Swedish company AstraZeneca to develop and test a coronavirus vaccine known as ChAdOx1 nCoV-19 or AZD1222. A large clinical trial showed the vaccine offered strong protection, with an overall efficacy of 79 percent.

Dozens of countries have authorized the vaccine for emergency use, but it is not yet authorized by the Food and Drug Administration. In March more than a dozen countries paused use of the vaccine over concerns about possible rare blood clots.

A Piece of the Coronavirus

The SARS-CoV-2 virus is studded with proteins that it uses to enter human cells. These so-called spike proteins make a tempting target for potential vaccines and treatments.

Spikes

Spike

protein

gene

CORONAVIRUS

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.


ReadMore: https://www.nytimes.com/interactive/2020/health/oxford-astrazeneca-covid-19-vaccine.html

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