The on-loan Udinese striker tapped in Watford's 20th-minute opener before unselfishly setting up Troy Deeney for the Hornets' second 14 minutes later.
And Czech Vydra rounded off the win 18 minutes from time with a composed flick as Gianfranco Zola's men registered a third successive win to improve their promotion prospects.
Burnley's own run of three victories in a row ended as they lost 2-1 at home to Birmingham, who move further away from the relegation zone as a result.
Curtis Davies (21) gave the visitors the lead and although Ross Wallace levelled the scores from the penalty spot 11 minutes into the second half, the Clarets had Dean Marney dismissed in the closing for a lunge and Marlon King made the extra man count with a last-minute winner.
Two goals from the promising Thomas Ince gave Blackpool a 2-1 win at Wolves - Dean Saunders' first defeat as boss of the Molineux club. Things looked bright for the home side when Sylvan Ebanks-Blake headed them into a 15th-minute lead - but Ince took advantage of hesitation from Roger Johnson to level the scores just before the break.
Ince got the winner in the 78th minute, before Johnson was dismissed at the end.
Jon Stead gave bottom club Bristol City a lift, with a late goal giving Sean O'Driscoll's side a 2-1 victory over former club Ipswich. Mick McCarthy's fellow strugglers got the reward their early endeavours deserved when Daryl Murphy scored on the half hour.
However, Steven Davies equalised two minutes into the second half and Stead's last-minute breakthrough proved decisive at Ashton Gate. Meanwhile, a late Sheffield Wednesday revival gave them a 2-1 success at mid-table Charlton which moves them clear of the bottom three.
Johnnie Jackson's 47th-minute goal gave Charlton the lead but Reda Johnson headed an equaliser six minutes from time and on-loan Swansea striker Leroy Lita's deflected shot won it a minute from time.
- Sports & Recreation
- Troy Deeney
- Curtis Davies