Is it possible for a vaccine to give a stronger immunity than infection with a live, non-attenuated virus?

You are either immune to a virus or you are not. There's no in-between. Some immunity can wear off over time, it's related to things called antigens. This is why 'booster' vaccines exist.

A vaccine is measured in its ability to prevent disease across a population, not in an individual. It's not a 'strong/weak' thing. A vaccine either will or won't prevent infection.

The flu vaccine is slightly different than most others because it's a predictive vaccine. They have to look at genetic and epidemiology info and guess which strain or strains will be highly infectious that 'season'. There are lots of different strains of flu and they change over time as well.

The CDC has a really great Google doc and info page on this stuff. It's a good place to start.

/r/askscience Thread