The Clarets made their numerical advantage count 10 minutes later as Vokes fired in his first of the afternoon from a Matt Lowton delivery.
It is not since March 2014 that Chelsea have had two players sent off in the same game in the Premier League and only the seventh occasion on which it has happened in their Premier League history.
The injury luck that afforded him the most settled XI in the division last season abandoned the Blues weeks ago and their lack of squad depth was achingly apparent against Burnley. We kept a good shape early in the game, but the sending off makes a big difference.
Vokes, who scored two of those goals in the first half, admits his side were sloppy to allow Chelsea back into the game but feels after an atrocious away record previous year, it was a huge result for the team and the club.
It wasn't to be the end of the first half scoring.
Asked whether he sensed the champions were vulnerable without Eden Hazard, Diego Costa, Pedro and Tiemoue Bakayoko, he added: "I don't think so".
Southampton had 29 shots on goal, with Manolo Gabbiadini and Dusan Tadic wasting the best of the chances. Disjointed and embarrassed in the first half, Chelsea threatened to mount the most unlikely of comebacks in a stirring second-half display, but just failed to overcome their numerical disadvantage. David Luiz scored a late consolation goal for the defending champions.
It's off to a disastrous start at Stamford Bridge as the Blues are now losing to lower table side Burnley at home.
"A lot was made of our away form last season", Vokes said. The Chelsea supporters vented their anger towards referee Pawson, while the delirious Burnley fans sang: "We are top of the league!"