Q1 - Should an adult be vaccinated... certainly the protection appears to outweigh any downside risk
Q2 - Should an adult get vaccinated if previously infected?, I think the research you link says yes that it will be helpful in some circumstances (and if there is no downside risk, why not?)
Q3 - Are there instances where an adult would not get vaccinated? I can certainly see reservations for a group such as pregnant women... so I generally hate the terms always/ never/ etc. there is still an element of choice
Q4 - What if I don't want to (and it's available)? Expect that there will be some restrictions on things that you can do... cruise perhaps? not if you don't have the vaccine... but the impact to others should be supported by data over time... and some people will need to be convinced. (If it just harms the individual, there will still be a choice question - people still drink, smoke, get fat...)
Again, thanks for the link