Wales' Six Nations clash against Scotland in Cardiff on Saturday has been postponed in a U-turn from Friday morning's insistence that the game would go ahead.
Less than five hours after the Welsh Rugby Union said the Principality Stadium encounter remained on, the governing body announced its postponement.
In its latest statement, the WRU said: "The Welsh Rugby Union has maintained an open dialogue with, and continued to seek advice and direction from, the Welsh Government and other stakeholders, including the Six Nations, on this fast-moving issue.
"Whilst medical advice remains consistent, we have decided that it is in the best interests of supporters, players and staff to fall in line with recent measures taken across the UK and global sports industries.
It becomes the fourth game to be postponed in this season's Six Nations.
Ireland's games against Italy and France had already been called off, in addition to England's appointment with Italy in Rome.
No dates for rearranged games have yet been announced, although late October is thought to be an option.
The Scotland squad, meanwhile, had arrived in Cardiff and trained at the Principality Stadium on Friday.
Had the game gone ahead, Wales captain Alun Wyn Jones would have equalled the world record held by New Zealand's World Cup-winning skipper Richie McCaw of 148 Test match appearances.
But that feat will now be put on hold probably until the summer, when Wales play Tests against New Zealand in Auckland and Wellington.
The WRU, meanwhile, said that Friday night's Six Nations Under-20 game between Wales and Scotland in Colwyn Bay will be played behind closed doors.