Wales' hopes of making it to next summer's finals through a top-two spot in Group E suffered a severe setback with a 1-0 defeat to Hungary in Budapest on Tuesday night.
It was Wales' second defeat in the space of four days after a 2-1 loss to Croatia on Saturday.
It leaves them six points behind group leaders Hungary, albeit with a game in hand, and three adrift of Slovakia – 5-1 winners in Azerbaijan on Tuesday – and Croatia.
"We've got an uphill task for the rest of the group but it's still doable – 100 per cent," Stoke striker Vokes said.
"Realistically we probably have to win all of our games now. But you've seen this group, everyone beats each other.
"The last two games we've had are probably the toughest in the group, and it's obviously disappointing not to get anything from them.
"But we've got these teams back in Cardiff now and we'll look to get something there. We've got Azerbaijan at home next in September and that will be huge for us."
Vokes provided a focal point in the closing stages as Wales frantically pushed for an equaliser at the Groupama Arena.
But it was to prove a frustrating night after Gareth Bale, who failed to provide the attacking spark that Wales needed, and Tom Lawrence had missed clear opportunities to open the scoring.
"I thought it was there for us, which is why it's so disappointing," Vokes said. "The second half could have gone either way, but I felt we were still the stronger side.
"Gareth has not had great game-time (at Real Madrid) but we know he is a match-winner for us. There's no doubts from the lads in the dressing room what he's got and what he's about."
Bale and Vokes are among the survivors from the squad that reached the semi-finals of Euro 2016 under previous Wales manager Chris Coleman.
Current boss Ryan Giggs has fast-tracked several youngsters into the side but he recalled experienced pair Ashley Williams and Chris Gunter to the defence in Budapest, the pair now having won 181 caps between them.
There was still a fresh feel to the starting line-up, however, with James Lawrence, Ethan Ampadu, David Brooks and Daniel James all relatively new to the international stage.
"You've seen the transition which has happened in the squad," Vokes said. "There's a lot of experience from those who have been here a while.
"But the lads coming through have got a lot of caps under their belts now. The group is what it is now, but we still believe we can do it when we come back after the summer."