Ulster will play their next two home games behind closed doors, having received new advice from Chief Medical Officer and Chief Scientific Advisor in Northern Ireland.
The province had welcomed a small number of supporters back for their Pro14 opener against Bennetton, with 600 supporters allowed into Ravenhill.
However, the worsening Covid-19 situation in the North has forced a rethink and Sunday's clash with Dragons along with November's showdown with Glasgow will not be played in an empty stadium.
The decision will be reviewed ahead of the Pro14 fixture at home to Scarlets on Sunday 22 November.
The development game follows last week's announcement that all rugby activity below elite level in Northern Ireland will be suspended for four weeks.