Corona Viruses have their own genetic code protected by a fatty envelope.
Because this family of virus has “spikes” of protein protruding from the envelope of fat, it has a “crown of thorns” appearance hence the name Corona virus. These spikes attach to our human cells and allow the virus protein to take over and make new virus that spread throughout the body causing the disease. The virus has a tendency to attack cells that line the blood vessels and cause clots. People with coronary artery disease, obesity and diabetes are particularly vulnerable to such an attack.
All three of the new vaccines have been developed to help the body to recognize the virus “spikes” and make protective antibodies to destroy the virus. If the body is exposed to the virus, the system is in place to make huge amounts of antibody to destroy the virus.
The Pfizer and Moderna vaccines have a tiny bit of genetic code, the RNA Spike protein code, that are introduced into our own cells to start the process of making antibody. These vaccines can not give you a virus infection. The RNA vaccines are very fragile and require very special handling. The AstraZeneca vaccine uses a harmless virus to introduce the spike protein genetic code into the host cells to start the production of protective antibody. This is the way most vaccines have worked in the past; the RNA vaccines are a new concept.
The Pfizer and Moderna vaccines produce 90%+ levels of protection from the Corona virus; this is outstanding. The AstraZeneca vaccine protects about 70% of immunized people which is still very impressive.
Because the Pfizer and Moderna vaccines are RNA vaccines, they are more fragile. In developed countries like Europe and North America this is not a major problem. In many parts of the world, a more robust vaccine like the AstraZeneca product will be the vaccine of choice.