One thing that in the past has taken a lot of time is proving the vaccine works 'in the wild'. Which means you vaccinate thousands of people and then wait a cou

One thing that in the past has taken a lot of time is proving the vaccine works 'in the wild'. Which means you vaccinate thousands of people and then wait a couple of years and see if they get infected or not. If they do, and that happens, your vaccine is bunk. Sometimes vaccines only provide short term immunity. Fading immunity is a problem with some vaccines. And you also monitor them to see if there are adverse effects. Too many adverse effects and you're vaccine isn't safe enough. Adverse effects are like anaphylactic shock, guillain barre syndrome. And that sometimes candidate vaccines both fail to provide protection but make the infection worse. There is a balancing act between how bad a disease and the risk you're willing to take with the vaccine. Covid19 is probably the worst. It's really dangerous to certain population groups like the elderly and people with certain health issues. And much less so to young healthy people. To get rid of covid19 we're going to have to vaccinate 90% of the world population which means the vaccine needs to be 100% safe. Anyway you should not be ashamed just because you don't know something.