Skipped to the bottom, ya boring ****Flu is influenza virus (various mutations)
Covid-19 is a coronavirus like SARS and MERS and I think 6 other types that present symptoms very much like the common cold in humans. Most people on the planet will catch at least one coronavirus in their lifetime without knowing its a coronavirus. Its widely considered that covid-19 will eventually settle down in to a milder infection much like the others that circulate in humans.
Other types of virus causing common colds symptoms are Rhinovirus, RSV and Parainfluenza.
The astrazeneca vaccine used a adenovirus which only infects chimpanzees. Adenovirus' can cause severe symptoms in humans including lung problems, pneumonia and conjunctivitis. It's a serious virus. The reason it was used? Simply that humans had no existing immunity to this particular strain so the vaccine would be the first infection which promotes a better response.
I know... I'm a boring ****.

