The U.S Embassy and Consulate in Nigeria has suspended the interview waiver “Drop Box” application process, effective May 14, 2019 and made this known on the official US Visa Application platform.
The Interview Waiver Program (IWP), also called the Visa Interview Waiver Program, is a program managed by the U.S. Department of State’s Bureau of Consular Affairs under which, under some circumstances, interview requirements can be waived for some non-immigrant visa applicants.
This means that if travel is necessary and your visa needs to be renewed, you must attend visa interviews like first timers.