Since he was on a bit of a break, Jason hadn't managed to resume yet when the COVID virus broke out within the squad.
As someone who had previously had COVID, he was at high risk of reinfection and his break was extended involuntarily.
Of course since he had also been vaccinated since then, he wasn't at the risk of a sever infection, keyword being severe.
It simply meant he could still be infected and was infact at high risk since it had been over a year since his initial infection, but the infection wouldn't be severe, however it could lead to persistent symptoms, also known as Long COVID.
If he really did get long COVID, then it would be like getting another long term injury because during the period he was showing symptoms, he was a carrier of the virus which meant long time quarantine.
Neither Jason nor Tottenham wanted first so Jason hadn't even gotten to breathe the air of the training grounds since his trip to Paris.
