The April 20 attack took place at the main gate of the hospital in the town of Khar, in the restive Bajaur tribal area.
Local administration official Abdul Haseeb said the attacker was a female “about 18-20 years old.”
He said the dead included a security worker, a hospital employee and two civilians.
There not immediate claims of responsibility for the attack.
Bajaur is one of seven districts that make up Pakistan’s Federally Administered Tribal Areas (FATA).