Vierge grew up in Barcelona and proved himself quickly in the FIM CEV Moto2 European Championship, finishing runner-up in 2015 with six race wins. He also began his Moto2 World Championship career that year, joining the Tech3 team as a permanent replacement from the tenth round onwards, though he did not score points in his debut season.
Vierge remained at Tech3 for 2016 and made his mark on the championship by scoring points in Argentina and reaching a best finish of eighth at Sepang. He accumulated 37 points and was awarded the Moto2 Rookie of the Year prize, edging out Miguel Oliveira by a single point. In 2017 he continued with Tech3, partnered by Remy Gardner. A chest injury in qualifying at Mugello and a broken arm in practice at Assen forced him out of multiple rounds, but he recovered to take his first Grand Prix podium — a second place at Motegi — and closed the season eleventh with 98 points.
For 2018 Vierge moved to Dynavolt Intact GP, where he immediately demonstrated his qualifying ability by taking his first pole position in Argentina. He finished second there, added a third place at Phillip Island, and ended the year eleventh with 131 points, his most productive Moto2 campaign to date. A crash with Steven Odendaal during qualifying in Austria sidelined him for that round and the following weekend at Silverstone.
The 2019 season with EG 0,0 Marc VDS proved difficult. Vierge qualified on the front row at Qatar and Argentina — consecutive pole positions to open the year — but mechanical trouble and first-lap incidents repeatedly denied him results. He managed only a best finish of fourth all season and dropped to thirteenth in the standings with 81 points. He had replaced Joan Mir, who moved up to MotoGP.
Vierge joined Petronas Sprinta Racing (Sepang Racing Team) for 2020 and 2021, partnering Jake Dixon in both years. The 2020 season returned no podiums despite a pole at Catalunya, with a best result of fourth at Rimini and a tenth-place championship finish on 79 points. In 2021 he secured one podium — third in Catalunya — and again finished eleventh on 93 points, 35 points clear of Dixon.
In September 2021, Vierge and Honda announced a move to the Superbike World Championship for 2022. He joined Honda Racing Corporation to replace Leon Haslam, partnering fellow Moto2 graduate Iker Lecuona on the factory CBR1000RR-R Fireblade. The pairing represented Honda's effort to rejuvenate its World Superbike programme with riders who had extensive Grand Prix experience.
In 2025, Vierge was unable to compete in the Suzuka 8 Hours after Japanese authorities declined to grant him a work visa. He had been scheduled to ride as a replacement for the injured Lecuona.
Vierge's career illustrates the challenge many strong qualifiers face in converting front-row pace into consistent race results. Two consecutive Moto2 pole positions to open 2019 with no corresponding wins underlined the gap between his one-lap speed and race-distance execution. His move to World Superbike with Honda offered a fresh competitive environment after seven seasons in the intermediate Grand Prix class.