Vaccines?

I have some baby chicks, ranging from 2 weeks old today, and I'd say maybe 3.5-4 weeks (not sure, that will be posted in a different thread).

I hatched one of the chicks myself, the one I know is 2 weeks, two came from a breeder 1.5 weeks ago, and the other one was adopted on Tuesday.
I got three to keep my first and only hatchling company; social animals wither away in solitude. However, one died 2 days after I got her. The man I bought them from wouldn't replace her. Not knowing why she died, I waited a week to check for signs of illness in the remaining chicks before adopting an Ameraucana from a girl who got bored with her chick after 3 days... (I'm sure this happens a lot, people suck).

I was wondering if I should vaccinate my chickens (hopefully there's a vet near where I live that does it, as chicken keeping has to be kept underground— my neighbors are okay with it though ). And if I should vaccinate, what vaccines should I get for my small flock of 4?

The adopted chick had the sniffles when I picked it up, and then the next day, all of them has the sniffles, however I've noticed that if they get cold is the only time they sneeze (especially on our breif outside "adventures"). The day after I adopted, the oldest chick had dumped the waterer over and the bedding (and chicks) were damp, so I'm assuming that's what did it. All are still active and appear healthy.

You don't need to vaccinate. Disease is spread bird to bird or by contamination from one flock to another via being tracked in on boots. Seriously, bio contamination spread by not changing clothes and shoes from one farm/flock to another. If you bring in new birds an area away from flock is advised for quarantine. You watch the new birds for three weeks or so to ensure they are not contagious and use different boots during this time. Saying this for future years and introduction of grown birds. Just keep in mind simple bio security and your flock will never have a problem.

Great, thanks!! The sniffles had me worried, but non of them are sneezing this morning, so it had to have just been they were cold.

They are on medicated chick feed, and I put a tiny bit of vitamins/electrolytes in the water for good measure.

The only other chickens I'll be in contact with ever will likely be already processed ones from the grocery Like I said, they're not allowed where I live, but I've heard of a few people in my city who have them.