What Is So Special About COVID-19’S Spike Protein

What is so special about COVID-19’s spike protein? Why are vaccine developers so interested in it?
What are some advantages to the new COVID-19 mRNA vaccine compared to previous vaccine technologies? What are some disadvantages?
Using credible sources, find the percent efficacy of the latest flu vaccine, and compare it to that of some of the most common COVID-19 vaccines (e.g. Pfizer, Moderna/BioNTech, Johnson & Johnson, AstraZeneca/Oxford etc.) Then, brainstorm and share with your peers some ideas about why you think the overall efficacy is higher for the COVID-19 vaccine. (Hint: the vaccines may target different things, but think about how the vaccine is produced)