A vigil will be held for Georgina Gharsallah on her 32nd birthday.
The mother-of-two was last seen at 9.30am on March 7, 2018, at the Clifton Food and Wine store in Clifton Road, Worthing.
CCTV footage of someone resembling Georgina by Subway in Chapel Road later that day has also been released.
The vigil will be on Tuesday from 7pm to 8pm outside the Guidbourne Centre in Worthing.
Guests will include investigative journalist Donal MacIntyre, who is making a podcast series on the case.