Inmates at the Vavuniya Prison administered the measles vaccine.
The Epidemiology Unit said all inmates at the Vavuniya Prison who had not received the measles vaccine were vaccinated.
The Unit said all necessary instructions have been given to control the spread of measles within the prison.
The Vavuniya Prison was temporarily closed after four inmates were diagnosed with measles.
The prison is off-limits since the 25th of July.
Prisons Spokesperson and Administrative Commissioner Chandana Ekanayake said that inmates are not allowed to meet with relatives, and visitation opportunities have been suspended.
The taking of detainees to courts for legal proceedings has also been temporarily stopped.
The number of inmates in Vavuniya Prison is over 400.