The team put Matz, who is asymptomatic, on the list a day after the left-hander beat the Red Sox. He allowed one run and four hits over 5 2/3 innings Saturday against Boston.
"He's still going through additional testing," Blue Jays manager Charlie Montoyo told reporters. "The guys that were around him that are vaccinated came back negative, and that's good news."
Matz has a 7-3 record and 4.26 ERA over 13 starts this season, his first with the Blue Jays. He spent his first six MLB seasons with the New York Mets before being traded to Toronto in January.
In 125 career games (120 starts) between the Mets and Blue Jays, Matz has compiled a 38-44 record and 4.34 ERA with 627 strikeouts.
Right-handed pitcher Jeremy Beasley was recalled from Triple-A Buffalo in a corresponding roster move.
The Blue Jays earned an 18-4 win over the Red Sox on Sunday. Toronto has a 33-30 record and sits third in the American League East this season.
The clubs wrap up their four-game series Monday night in Boston.