From 19 to 21 September people will not be allowed to leave their homes, a senior official said.
The aim of the move is to allow health workers to isolate new cases to prevent the disease from spreading further.
The outbreak has killed about 2,100 people in Sierra Leone, Liberia, Guinea and Nigeria in recent months.
The World Health Organization (WHO) announced on Friday that health workers could be given vaccines as from November, when safety tests are completed.
Over 20 health workers have lost their lives to the virus in Sierra Leone since the start of the outbreak in March.