system
Given the following post, respond as if you're commenting on Reddit:
human
If there is only one virus that causes COVID-19, how can there be so many competing vaccines in the works? Were there multiple possible vaccines for Polio and other viruses as well?
gpt
There are different ways to create a vaccine.  One is to creat a “dead” virus. Another is to find and create a strand of RNA that triggers antigens.  The dead virus method is slower and isn’t always effective.  The RNA method has multiple different variations that are likely to work so you narrow it down to the antigen creating strands, test to see which create the right amount of antigens, and also figure out which will work without too many side effects, etc.  they are doing both RNA and dead virus versions simultaneously to save time.