How do whole virus vaccines trigger immunity?

Both live attenuated and inactivated vaccines contain the whole or part of the disease-causing pathogen, but the type of immunity they trigger is slightly different.

Live attenuated vaccines are derived from viruses that have been weaked under laboratory conditions, so that when injected they will infect cells and replicate but cause no or only very mild disease. They may be unsuitable for people with compromised immune systems (e.g. those with HIV) and pregnant woman though, because even in a weakened virus may trigger disease in vaccinated individuals or their contacts. This has been for vaccine derived poliovirus associated with the oral vaccine.