The Bears starting quarterback, Jay Cutler, also missed the game due to a concussion, so Campbell made his 76th career start.
Kaepernick, a second-round draft pick out of Nevada last year, entered the game with 241 passing yards to 14,511 for Campbell. Kaepernick compiled a 133.1 passer rating, and he was sacked just once.
“I wanted to come out and show what I was capable of doing, show I could be a starter,” Kaepernick said.
Campbell went 14 of 22 for 107 yards with one touchdown, two interceptions and a 52.7 passer rating. Campbell was sacked six times, 5 1/2 of those by outside linebacker Aldon Smith.
The 5 1/2 sacks broke the record for a Monday night game.
Aldon Smith abused Bears tackles J’Marcus Webb and Gabe Carimi as he took over the NFL sack lead with 15.
“It was very hard,” Campbell said. “It was definitely not the way we prepared all week, to come out and have this kind of performance. You know their defense is great. They do what they do best. They rush pretty well, they hit pretty well and they cover pretty well, but it was definitely not our best effort by any means.”
The 49ers improved to 7-2-1 and increased their lead over 6-4 Seattle in the NFC West. Chicago, which lost at Candlestick for the eighth straight time, fell to 7-3 and into a first-place tie with Green Bay in the NFC North.
“Tough night for us,” Bears coach Lovie Smith said. “You have to give the 49ers a lot of credit. They started fast and kept us off balance all night.
”They had a quarterback that hadn’t played a lot, but he was on. He looked like a seasoned vet.“
Monday night’s game featured the NFL’s two stingiest defenses based on points allowed. The 49ers were ranked No. 1, allowing just 14.1 points per game, and the Bears were No. 2 at 14.8.
Kaepernick and the 49ers had 20 points by halftime, while the Bears were scoreless.
Going into the game, there was plenty of debate about which team had the better defense.
”I think obviously we came out and proved a point,“ Aldon Smith said. ”I think tonight we showed who it was.“
The 49ers extended their lead to 27-0 with 11:05 left in the third on Kaepernick’s 10-yard touchdown pass to Michael Crabtree.
The Bears finally scored with 3:43 left in the third on Campbell’s 13-yard touchdown pass to Brandon Marshall, cutting San Francisco’s lead to 27-7. But late in the third quarter, Campbell overthrew Earl Bennett, and 49ers safety Dashon Goldson intercepted at the Chicago 37-yard line. David Akers’ 32-yard field goal made it 30-7 with 11:46 remaining.
The 49ers increased their lead to 32-7 with a safety with 9:32 remaining.
Tight end Vernon Davis had a big night for the 49ers, catching six passes for 83 yards and a touchdown.
”I thought Colin did a very good job getting Vernon the ball,“ Harbaugh said. ”I think Vernon did a great job getting open.“
San Francisco rolled up 249 yards of total offense in the first half to just 35 for the Bears.
Kaepernick was 12-for-15 for 184 yards and a touchdown before halftime. Campbell was 4-for-8 for 21 yards and one interception in the first half, and he was sacked three times — each by Aldon Smith.
Kaepernick completed seven of his first eight throws for 114 yards and his first NFL touchdown pass, leading the 49ers to a 10-0 lead. At that point, he had a perfect passer rating of 158.3. So much for nerves.
Kaepernick learned Sunday night that he would start. Smith was officially ruled out on Monday.
”It just felt good to be back out on the football field playing,“ Kaepernick said. ”I thought we did a good job as an offense putting points on the board.“
The 49ers took the opening kickoff and marched 68 yards in nine plays for Akers’ 32-yard field goal, grabbing a 3-0 lead. Kaepernick was 4-for-5 for 45 yards on the drive, connecting with Davis twice for a total of 34 yards.
The Bears went three-and-out as Aldon Smith sacked Campbell on third-and-2 from the 28, forcing a punt. Kaepernick went back to work. On third-and-7 from his 40, Kaepernick lofted a 57-yard pass down the right sideline that hit wide receiver Kyle Williams in stride.
Williams beat nickel cornerback Kelvin Hayden on the play, and Chris Conte made a touchdown-saving tackle at the 3. On first-and-goal, Kaepernick connected with Davis — wide open in the right corner of the end zone — for a 3-yard touchdown pass with 6:14 left in the first quarter.
The 49ers forced another Chicago punt late in the first quarter and drove 96 yards in eight plays for another touchdown. Kendall Hunter scored on a 14-yard burst up the middle, increasing the 49ers’ lead to 17-0 with 12:40 left in the half.
Frank Gore carried three times for 33 yards on the drive, and Kaepernick hit Davis on a 32-yard pass.
The 49ers’ defense quickly got the ball back for Kaepernick. Campbell tried to hit wide receiver Devin Hester along the left sideline, but 49ers cornerback Tarell Brown cut in front for an easy interception and it returned 5 yards to the Chicago 44.
The 49ers drove to the Bears’ 12-yard line but backtracked. After Kaepernick was sacked by Corey Wootton and Israel Idonije on third down, San Francisco settled for a 37-yard Akers field goal. The boot put the 49ers ahead 20-0 with 6:32 left in the half.
”You know tonight was probably the worst nightmare, but we just got to find a way,“ Campbell said. ”It’s just one game that we lost, but we got to pick it back up next week, try to get back on the winning side of things. Our goals and everything are still set ahead of us. We have to start improving and improving quickly.“
NOTES: Bears rookie wide receiver Alshon Jeffery was active after missing four games with a fractured right hand, but he left the game midway through the second half with a knee injury and did not return. ... Chicago defensive end Shea McClellin, who suffered a concussion last week against Houston, was inactive. Bears defensive lineman Amobi Okoye suited up after missing the previous three games. ... Bears nickel back D.J. Moore was inactive for the first time this season. ... Cutler and McClellin did not make the trip to San Francisco. ... San Francisco running back Brandon Jacobs, who has yet to play a down this season, was inactive again.