If you are asking about vaccinations, many people get their chickens vaccinated for Mareks disease, some for coccidiosis. Later some will get fowl pox vaccines if it you live in a warm environment with mosquitos. There are others such as for respiratory diseases such as MG, coryza, ILT, and IB. Some hatcheries such as Murray McMurray have a list of vaccines available on their website. I will only get mine vaccinated for Mareks if they are from a hatchery--it only costs a dollar or less, and it is a very devastating disease that will infect and other chickens you get.
Well, chicks don't always get vaccinations/shots. But many people have them vaccinated for Marek's Disease, Coccidiosis, and/or a respiratory disease like Newcastle, Bronchitis, or Infectious Larayngotracheitis. Fowl Pox is another vaccine that can be given to older birds, too.