49ers 32, Bears 7: Colin Kaepernick was brilliant in his first career start, throwing a pair of touchdown passes to lead host San Francisco to a rout of Chicago.

Kaerpernick, playing in place of the injured Alex Smith, completed 16 of 23 passes for 243 yards and sparked the 49ers (7-2-1) to a 20-0 halftime lead in easily winning the matchup of backup quarterbacks against beleaguered Bears signal caller Jason Campbell.

Aldon Smith registered 5.5 of the six sacks against Campbell, who was intercepted twice and fumbled for a safety in a dominating defensive performance by San Francisco that opened a 1 1/2-game lead atop the NFC West. Chicago (7-3) suffered its second straight loss and dropped into a tie with Green Bay atop the NFC North.

Tight end Vernon Davis had six receptions for 83 yards and a touchdown and David Akers kicked three field goals for the 49ers, who scored the first 27 points and limited the Bears to 35 total yards in the opening half.

Kendall Hunter scored on a 14-yard run in the second quarter and Kaepernick connected with Michael Crabtree on a 10-yard scoring pass as the lead ballooned to 27-0 with 11:12 left in the third quarter.

Chicago had not allowed points on an opening drive this season, but Kaepernick ended that streak by moving his team 68 yards in nine plays, leading to Akers' 32-yard field goal. Kaepernick needed only four plays to reach the end zone on the ensuing possession, connecting with Davis on a 3-yard scoring toss that was set up by a 57-yard pass to Kyle Williams to make it 10-0 with 6:19 left in the first quarter.

GAME NOTEBOOK: Campbell, who finished 14-of-22 for 107 yards and a touchdown, had minus passing yards until completing an 18-yarder to Michael Bush midway through the third quarter. ... The game marked the first time in NFL history that both quarterbacks were making their first starts for division-leading clubs this late in the season. ... Smith took over the league lead with 15 sacks and has 29 in his first two seasons - the third most all-time for a player in his first two years since 1982.