Goals in each half from Vlahovic and another in the 26th minute from strike partner Federico Chiesa at the Allianz Stadium pushed Juve a point ahead of both Milan clubs before the derby which kicks off later.
Inter Milan and AC Milan are both on a perfect nine points heading into their clash for local bragging rights, one behind Juve.
Massimiliano Allegri's Juve will concede top spot regardless of the result at the San Siro but the coach will be encouraged by what he saw in front of an enthusiastic home crowd in Turin.
"Last season was very difficult but despite all that we did OK," said Vlahovic of the previous campaign in which Juve were docked 10 points for illicit transfer activity.
"Now we are more fired up and have a point to prove... our aim is to be in the top four and we will do everything we can to make it happen."
Allegri has paired Vlahovic and Italy star Chiesa up front this season and the attacking duo have hit it off, combining for seven goals in unbeaten Juve's opening four matches.
Chiesa, who missed Italy's two recent Euro 2024 qualifiers with a muscle problem, has started the domestic season in great form after struggling with injuries in recent years.
"We're really good friends, we've known each other a long time," added Vlahovic of Chiesa, with whom he also played at Fiorentina.
"We're really happy to have him fit and healthy."
Lazio, who scored through a beautiful 64th-minute Luis Alberto curler, just before Vlahovic netted his second, are 15th following their third defeat of the season.
Italian anti-doping authority NADO said Monday that Pogba showed elevated levels of testosterone in tests after Juve's season opener at Udinese.
World Cup winner Pogba, who risks a four-year ban, was questioned in a Paris court on Friday alongside five acquaintances and childhood friends suspected of trying to extort 13 million euros from him.
Bonucci claimed on Wednesday that Juve violated professional football's collective bargaining agreement by sidelining him over the summer before he moved to Union Berlin in Germany at the end of the transfer window.